Regarding select single and select upto 1 rows

hi experts,
plz let me know about difference between select single and select upto 1 rows with small eg...
thnx in advance.

Hi Ravi,
According to SAP Performance course the SELECT UP TO 1 ROWS is faster than SELECT SINGLE because you are not using all the primary key fields.
select single is a construct designed to read database records with primary key. In the absence of the primary key, it might end up doing a sequential search, whereas the select up to 1 rows may assume that there is no primary key supplied and will try to find most suitable index.
The best way to find out is through sql trace or runtime analysis.
Use "select up to 1 rows" only if you are sure that all the records returned will have the same value for the field(s) you are interested in. If not, you will be reading only the first record which matches the criteria, but may be the second or the third record has the value you are looking for.
The System test result showed that the variant Single * takes less time than Up to 1 rows as there is an additional level for COUNT STOP KEY for SELECT ENDSELECT UP TO 1 ROWS.
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause If this results in multiple records then only the first one will be returned and therefore may not be unique.
Mainly: to read data from
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns the first record of the result set.
Mainly: to check if entries exist.
Select Single is the best one compared to UPto one rows.
Select Single will get the first record from the table which satisfies the given condition.So it will interact once with the database.
UTO 1 rows will get the list of the records for the given match and iwll show the first record from the list.So it will take time to get the record.
SELECT SINGLE VBELN from VBAK
where MATNR = '1M20'.
---Thjis will get the first matched record and will display the record
SELECT VBELN from VBAK
where MATNR = '1M20' upto 1 rows.
---Thjis will get the list of matched records and will display the first record
The Major difference between Select Single and Select UPTO 1 rows is The Usage Of Buffer for each.
Select Single will search for all the satisfied data and bring all that data into Buffer and later it will give to that data to the program.
Select UPTO 1 Rows will end the search after getting the 1st satisfied record and gives that record to the program.
Thus Select Single will take much processing time when compare with Select UPTO 1 rows.
Also
check these threads..
Difference between Select Single and Selct upto 1 row
Difference between Select Single and Select upto 1 row
Thanks,
Reward If Helpful.

Similar Messages

Select Single * and Select upto one row

Hi all,
Can anybody tell me what is difference between Select single * and select upto one row?
And which one is better?
Thanks in advance.......

According to SAP Performance course the SELECT UP TO 1 ROWS is faster than SELECT SINGLE because you are not using all the primary key fields.
select single is a construct designed to read database records with primary key. In the absence of the primary key, it might end up doing a sequential search, whereas the select up to 1 rows may assume that there is no primary key supplied and will try to find most suitable index.
The best way to find out is through sql trace or runtime analysis.
Use "select up to 1 rows" only if you are sure that all the records returned will have the same value for the field(s) you are interested in. If not, you will be reading only the first record which matches the criteria, but may be the second or the third record has the value you are looking for.
The System test result showed that the variant Single * takes less time than Up to 1 rows as there is an additional level for COUNT STOP KEY for SELECT ENDSELECT UP TO 1 ROWS.
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause If this results in multiple records then only the first one will be returned and therefore may not be unique.
Mainly: to read data from
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns the first record of the result set.
Mainly: to check if entries exist.
Select Single is the best one compared to UPto one rows.
Select Single will get the first record from the table which satisfies the given condition.So it will interact once with the database.
UTO 1 rows will get the list of the records for the given match and iwll show the first record from the list.So it will take time to get the record.
SELECT SINGLE VBELN from VBAK
where MATNR = '1M20'.
---Thjis will get the first matched record and will display the record
SELECT VBELN from VBAK
where MATNR = '1M20' upto 1 rows.
---Thjis will get the list of matched records and will display the first record
The Major difference between Select Single and Select UPTO 1 rows is The Usage Of Buffer for each.
Select Single will search for all the satisfied data and bring all that data into Buffer and later it will give to that data to the program.
Select UPTO 1 Rows will end the search after getting the 1st satisfied record and gives that record to the program.
Thus Select Single will take much processing time when compare with Select UPTO 1 rows.
Also
check these threads..
Difference between Select Single and Selct upto 1 row
Difference between Select Single and Select upto 1 row
Difference between select single and select upto one row
Difference between 'select single *' and 'select upto 1 rows'
difference between select single and select up to 1 rows
regards,
srinivas
*reward for useful answers*

Select single and select upto 1 rows

Hi
What is the difference between select single and select upto 1 rows
Performance wise which one is the best
Regards,
Maya

Hi,
Difference Between Select Single and Select UpTo One Rows
According to SAP Performance course the SELECT UP TO 1 ROWS is faster than SELECT SINGLE because you are not using all the primary key fields.
select single is a construct designed to read database records with primary key. In the absence of the primary key, it might end up doing a sequential search, whereas the select up to 1 rows may assume that there is no primary key supplied and will try to find most suitable index.
The best way to find out is through sql trace or runtime analysis.
Use "select up to 1 rows" only if you are sure that all the records returned will have the same value for the field(s) you are interested in. If not, you will be reading only the first record which matches the criteria, but may be the second or the third record has the value you are looking for.
The System test result showed that the variant Single * takes less time than Up to 1 rows as there is an additional level for COUNT STOP KEY for SELECT ENDSELECT UP TO 1 ROWS.
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause If this results in multiple records then only the first one will be returned and therefore may not be unique.
Mainly: to read data from
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns the first record of the result set.
Mainly: to check if entries exist.
reward points if useful
regards,
ANJI

Defference between select single and select upto 1 row?

What is the Defference between select single and select upto 1 row?

Hi,
Difference Between Select Single and Select UpTo One Rows
According to SAP Performance course the SELECT UP TO 1 ROWS is faster than SELECT SINGLE because you are not using all the primary key fields.
select single is a construct designed to read database records with primary key. In the absence of the primary key, it might end up doing a sequential search, whereas the select up to 1 rows may assume that there is no primary key supplied and will try to find most suitable index.
The best way to find out is through sql trace or runtime analysis.
Use "select up to 1 rows" only if you are sure that all the records returned will have the same value for the field(s) you are interested in. If not, you will be reading only the first record which matches the criteria, but may be the second or the third record has the value you are looking for.
The System test result showed that the variant Single * takes less time than Up to 1 rows as there is an additional level for COUNT STOP KEY for SELECT ENDSELECT UP TO 1 ROWS.
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause If this results in multiple records then only the first one will be returned and therefore may not be unique.
Mainly: to read data from
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns the first record of the result set.
Regards,
Priya.

Diff bw select single * and select upto one row

hai,
what is the difference between select single * and select upto one row.

hi,
ex code
Report Z_Difference
Message-id 38
Line-Size 80
Line-Count 0
No Standard Page Heading.
Start-Of-Selection.
Data: w_Single type Posnr,
t_Rows type standard table of Posnr
initial size 0
with header line.
Select single Posnr
from zDifference
into w_Single.
Select Posnr
into table t_Rows
from zDifference
up to 1 rows
order by Posnr descending.
Write :/ 'Select single:', w_Single.
Skip 1.
Write :/ 'Up to 1 rows :'.
Loop at t_Rows.
Write t_Rows.
EndLoop.
According to SAP Performance course the SELECT UP TO 1 ROWS is faster than SELECT SINGLE because you are not
using all the primary key fields.
select single is a construct designed to read database records with primary key. In the absence of the primary key,
it might end up doing a sequential search, whereas the select up to 1 rows may assume that there is no primary key
supplied and will try to find most suitable index.
The best way to find out is through sql trace or runtime analysis.
Use "select up to 1 rows" only if you are sure that all the records returned will have the same value for the field(s)
you are interested in. If not, you will be reading only the first record which matches the criteria, but may be the
second or the third record has the value you are looking for.
The System test result showed that the variant Single * takes less time than Up to 1 rows as there is an additional
level for COUNT STOP KEY for SELECT ENDSELECT UP TO 1 ROWS.
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause
If this results in multiple records then only the first one will be returned and therefore may not be unique.
Mainly: to read data from
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that
are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns
the first record of the result set.
Mainly: to check if entries exist.
You can refer to the below link..
http://www.sap-img.com/abap/difference-between-select-single-and-select-upto-one-rows.htm
rgds
anver
if hlped pls mark points

Regarding select single and select upto???

HI All,
Cud u pls let me know the differences between select single and select upto??
and which is the better option?? pls its quite urgent..plss plss
plss
Thanx in Advance
Prasad

Hi..,
According to SAP Performance course the SELECT UP TO 1 ROWS is faster than SELECT SINGLE because you are not using all the primary key fields.
select single is a construct designed to read database records with primary key. In the absence of the primary key, it might end up doing a sequential search, whereas the select up to 1 rows may assume that there is no primary key supplied and will try to find most suitable index.
The best way to find out is through sql trace or runtime analysis.
Use "select up to 1 rows" only if you are sure that all the records returned will have the same value for the field(s) you are interested in. If not, you will be reading only the first record which matches the criteria, but may be the second or the third record has the value you are looking for.
The System test result showed that the variant Single * takes less time than Up to 1 rows as there is an additional level for COUNT STOP KEY for SELECT ENDSELECT UP TO 1 ROWS.
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause If this results in multiple records then only the first one will be returned and therefore may not be unique.
Mainly: to read data from
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns the first record of the result set.
Mainly: to check if entries exist.
Check this example ...
DATA: gv_vbeln TYPE vbak-vbeln,
gv_erdat TYPE vbak-erdat.
SELECT SINGLE vbeln erdat
FROM vbak
INTO (gv_vbeln, gv_erdat)
WHERE erdat = '12/01/2006'.
SELECT vbeln erdat
FROM vbak UP TO 1 ROWS
INTO (gv_vbeln, gv_erdat)
ORDER BY erdat ASCENDING.
ENDSELECT.
*In the example, the select single gets the first record that satisfies the WHERE clause unlike in the UP TO 1 ROWS where it sorts the database records by the earliest date and gets its VBELN.
Try using the ORDER BY clause in SELECT SINGLE .. It gives an error !! U cannot use that with SELECT SINGLE
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause If this results in multiple records then only the first one will be returned and therefore may not be unique.
Hope u understood !!
reward if it helps u..
sai ramesh

Diff between select single and select upto 1 rows.

Hello aLL,
PL tell what is technical diff between select single and select upto 1 rows and how it is affecting the performance.
Rushikesh

Hi
Knowing when to use SELECT SINGLE or SELECT ... UP TO 1 ROWS
A lot of people use the SELECT SINGLE statement to check for the existence of a value in a database. Other people prefer to use the 'UP TO 1 ROWS' variant of the SELECT statement.
So what's the difference between using 'SELECT SINGLE' statement as against a 'SELECT .... UP TO 1 ROWS' statement ?
If you're considering the statements
SELECT SINGLE field INTO w_field FROM table.
and
SELECT field INTO w_field FROM table UP TO 1 ROWS. ENDSELECT.
then looking at the result, not much apart from the extra ENDSELECT statement. Look at the run time and memory usage and they may be worlds apart.
Why is this ?? The answer is simple.
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause If this results in multiple records then only the first one will be returned and therefore may not be unique.
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns the first record of the result set.
Get the difference ??
If not, here is a good example, credit for this example goes to Richard Harper, a friend of mine on sapfans.com :
Create a Ztable called ZDifference with 2 fields in it, MANDT of type MANDT and POSNR of type POSNR. Make sure both of these are keys. Also create a table maintenance dialog for it (SE11->Utilities->Table Maintenance Generator). Fill the table with ten rows 000001-000010.
Then run the program shown below:
Code:
Program: Z_Difference
Purpose: A program that demonstrates the difference
between SELECT SINGLE and SELECT UP TO n ROWS.
This program requires the data table Z_DIFFERENCE
to have been created according to the structure
outlined in the text above and populated with
at least 10 records.
Creation Date: 21/04/2004
Requested By:
Reference Doc:
Author: R Harper
Modification History:
Date Reason Transport Who
Report Z_Difference
Message-id 38
Line-Size 80
Line-Count 0
No Standard Page Heading.
Start-Of-Selection.
Data: w_Single type Posnr,
t_Rows type standard table of Posnr
initial size 0
with header line.
Select single Posnr
from zDifference
into w_Single.
Select Posnr
into table t_Rows
from zDifference
up to 1 rows
order by Posnr descending.
Write :/ 'Select single:', w_Single.
Skip 1.
Write :/ 'Up to 1 rows :'.
Loop at t_Rows.
Write t_Rows.
EndLoop.
You should see the output:
Select single: 000001
Up to 1 rows : 000010
The first 'SELECT' statement selected the first record in the database according to any selection criterion in the 'WHERE' clause. This is what a 'SELECT SINGLE' does. The second 'SELECT' has asked the database to reverse the order of the records before returning the first row of the result.
In order to be able to do this the database has read the entire table, sort it and then return the first record. If there was no ORDER BY clause then the results would have been identical (ie both '000001') but the second select if given a big enough table to look at would be far slower.
Note that this causes a problem in the Extended Program Check if the full key is not specified in a 'SELECT SINGLE'. Replacing the 'SELECT SINGLE' by an "UP TO 1 ROWS" will give the same exact results without any warning but the program will run slower and consume more memory. This is a good example of a warning that we should ignore... considering you are sure of what you are doing !!

Select single and select upto

what is the difference of select single and select upto statements

HI,
SELECT UP TO 1 ROWS is faster than SELECT SINGLE because you are not using all the primary key fields.
select single is a construct designed to read database records with primary key. In the absence of the primary key, it might end up doing a sequential search, whereas the select up to 1 rows may assume that there is no primary key supplied and will try to find most suitable index.
The best way to find out is through sql trace or runtime analysis.
Use "select up to 1 rows" only if you are sure that all the records returned will have the same value for the field(s) you are interested in. If not, you will be reading only the first record which matches the criteria, but may be the second or the third record has the value you are looking for.
The System test result showed that the variant Single * takes less time than Up to 1 rows as there is an additional level for COUNT STOP KEY for SELECT ENDSELECT UP TO 1 ROWS.
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause If this results in multiple records then only the first one will be returned and therefore may not be unique.
Mainly: to read data from
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns the first record of the result set.
Mainly: to check if entries exist.

Select single and select

hi everybody
what is the exact difference between select single vbeln and select vbeln
In what situations i should use these select single vbeln or select vbeln
regards
hridhayanjili.

Hai
Go through the following Document
According to SAP Performance course the SELECT UP TO 1 ROWS is faster than SELECT SINGLE because you are not
using all the primary key fields.
select single is a construct designed to read database records with primary key. In the absence of the primary key,
it might end up doing a sequential search, whereas the select up to 1 rows may assume that there is no primary key
supplied and will try to find most suitable index.
The best way to find out is through sql trace or runtime analysis.
Use "select up to 1 rows" only if you are sure that all the records returned will have the same value for the field(s)
you are interested in. If not, you will be reading only the first record which matches the criteria, but may be the
second or the third record has the value you are looking for.
The System test result showed that the variant Single * takes less time than Up to 1 rows as there is an additional
level for COUNT STOP KEY for SELECT ENDSELECT UP TO 1 ROWS.
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause
If this results in multiple records then only the first one will be returned and therefore may not be unique.
Mainly: to read data from
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that
are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns
the first record of the result set.
Mainly: to check if entries exist.
You can refer to the below link..
http://www.sap-img.com/abap/difference-between-select-single-and-select-upto-one-rows.htm
Regards
Sreeni

Select single n   select upto

frends please provide me the detail document and scenarios where we use with examples about select single and select upto n rows ?

Hi,
A lot of people use the SELECT SINGLE statement to check for the existence of a value in a database. Other people prefer to use the 'UP TO 1 ROWS' variant of the SELECT statement.
So what's the difference between using 'SELECT SINGLE' statement as against a 'SELECT .... UP TO 1 ROWS' statement ?
If you're considering the statements
SELECT SINGLE field INTO w_field FROM table.
and
SELECT field INTO w_field FROM table UP TO 1 ROWS. ENDSELECT.
then looking at the result, not much apart from the extra ENDSELECT statement. Look at the run time and memory usage and they may be worlds apart.
Why is this ?? The answer is simple.
The 'SELECT SINGLE' statement selects the first row in the database that it finds that fulfils the 'WHERE' clause If this results in multiple records then only the first one will be returned and therefore may not be unique.
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns the first record of the result set.
Get the difference ??
If not, here is a good example, credit for this example goes to Richard Harper, a friend of mine on sapfans.com :
Create a Ztable called ZDifference with 2 fields in it, MANDT of type MANDT and POSNR of type POSNR. Make sure both of these are keys. Also create a table maintenance dialog for it (SE11->Utilities->Table Maintenance Generator). Fill the table with ten rows 000001-000010.
Then run the program shown below:
Report Z_Difference
       Message-id 38
       Line-Size 80
       Line-Count 0
       No Standard Page Heading.
Start-Of-Selection.
Data: w_Single type Posnr,
        t_Rows   type standard table of Posnr
                 initial size 0
                 with header line.
Select single Posnr
    from zDifference
    into w_Single.
Select Posnr
    into table t_Rows
    from zDifference
   up to 1 rows
   order by Posnr descending.
   Write :/ 'Select single:', w_Single.
   Skip 1.
   Write :/ 'Up to 1 rows :'.
   Loop at t_Rows.
        Write t_Rows.
   EndLoop.
You should see the output:
Select single: 000001
Up to 1 rows : 000010
The first 'SELECT' statement selected the first record in the database according to any selection criterion in the 'WHERE' clause. This is what a 'SELECT SINGLE' does. The second 'SELECT' has asked the database to reverse the order of the records before returning the first row of the result.
In order to be able to do this the database has read the entire table, sort it and then return the first record. If there was no ORDER BY clause then the results would have been identical (ie both '000001') but the second select if given a big enough table to look at would be far slower.
Note that this causes a problem in the Extended Program Check if the full key is not specified in a 'SELECT SINGLE'. Replacing the 'SELECT SINGLE' by an "UP TO 1 ROWS" will give the same exact results without any warning but the program will run slower and consume more memory. This is a good example of a warning that we should ignore... considering you are sure of what you are doing !!
Regards,
Ferry Lianto

Select Single Vs Select upto 1 row

Hi All,
Please tell me which of the two statements is better if we want to retrieve only one record from a table.
Select single or Select upto 1 rows?
Regards,
Saurabh

There is a lot of confusion in the replies and also in the other thread.
If yoou ask 'A versus B' then this implies that you can use both for the same task, which is here not really true.
SELEC SINGLE should be used for SELECT with full primary key. where only 1 record CAN come back.
UP TO 1 ROWS is the special case of UP TO n ROWS can be used with any WHERE condition and gives you the first record which is found.
>The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the
> relevant records that are defined by the WHERE clause or lack of, applies any aggregate,
> ordering or grouping functions to them and then returns the first record of the resultant result
> set.
This in incorrect, the UP TO n ROWS does not read all, only if the ORDER BY is added, then you will get the first records in sort order which requires that all rfecords are read.
If you use UP TO 1 ROWS with a WHERE condition which is fulfilled by many records, then the first record is usually found very fast, even faster than a SELECT SINGLE.
If you use UP TO 1 ROWS or SELECT SINGLE with the same WHERE condition, then both are more or less the same.
Siegfried

"select count(*)" and "select single *" returns different result

Good day!
product version SAP ECC 6.0
oracle10
data transfers from external oracle db into customer tables using direct oracle db link
sometimes I get case with different results from 2 statements
*mytable has 10 rows
*1st statement
data: cnt type I value 0.
select count( * ) into cnt from mytable WHERE myfield_0 = 123 and myfield_1 = '123'.
*cnt returns 10 - correct
*2nd statement
select single * from mytable WHERE myfield_0 = 123 and myfield_1 = '123'.
*sy-dbcnt returns 0
*sy-subrc returns 4 - incorrect, 10 rows are "invisible"
but
1. se16 shows correct row number
2. I update just one row from "invisible" rows using se16 and 2nd statement returns correct result after that
can not understand why
thank you in advance.

Thank you, Vishal
but,
general problem is that
1. both statements have the same WHERE conditions
2. 1st return resultset with data (sy-dbcnt=10), 2nd return empty dataset, but must return 1 in sy-dbcnt
Yes, different meaning, you are right, but must 2nd must return 1, because of "select single *" construction, not 0.
Dataset to process is the same, WHERE conditions are equal...
I think the problem is that how ABAP interperets select count(*) and "select single *".
Maybe "select count (*)" scans only PK from index page(s)? and "select single *" scans data pages? and something is wrong with that?
I'm new in SAP and didn't find any SAP tool to trace dump of data and indexes pages with Native SQL.
se16 shows all records.
And why after simple manual update of just one record using se16 "select single *" returns 1?
I've just marked one row to update, didn't change any data, then pressed "save".

Diff b/w select endselect and select into table............

what is the difference b/w
Select
Endselect
and select into table....
Akshitha..

Hi,
When ever u want to append data into the workarea then use select ... endselect. When u r appending data into the internal table then use select. Also when u use select single then also use only select.
Eg: Using only Select
data : begin of itab occurs 0,
lifnr like lfa1-lifnr,
end of itab.
select single lifnr from lfa1 into itab.
data itab like lfa1 occurs 0 with header line.
select * from lfa1 into table itab.
Eg: Using Select .. endselect.
data : itab like lfa1 occurs 0,
wa like lfa1.
select * from lfa1 into wa.
append wa to itab.
endselect.
Regards

Select single vs select upto one rows only by experts

Hello Experts,
I am sorry to post this thread again , it is million times answered.
There is a lot of confusion in the answers, so we want a very clear and justifiable answer.
please dont post rubish answers by simply copying and pasting from other threads .
now i will give an example of 2 threads which i seen in the forum.
1) first thread is like this....
According to SAP Performance course the SELECT UP TO 1 ROWS is faster than SELECT SINGLE because you are not using all the primary key fields.
Select single is a construct designed to read database records with primary key. In the absence of the primary key, it might end up doing a sequential search, whereas the select up to 1 rows may assume that there is no primary key supplied and will try to find most suitable index.
2)second post is like this....
When it comes to performance..select ..up to 1 rows is faster than select single....
why?
B'coz, during a select single, the query always hits the database and reads the entire table into memory and fetches the matching single record for you in the memory,
where as in the case of select up to 1 rows, the query goes to the memory first if found it retrieves the record from there, otherwise the query hits the database.
3)i seen an simple example in se30 in tips and tricks it shown select single is having better performance than select upto...rows,
We all really value the best answers..

hi this is the standard one from the sdn..which will clear the answer..
https://www.sdn.sap.com/irj/sdn/wiki?path=/display/home/difference%2bbetween%2bselect%2bsingle%2band%2bselect%2bupto
regards,
venkat

Basic query regarding work-area and select query

hi
dear sdn members,
thanks too all for solving all my query's up till now
i am stuck in a problem need help
1) why basically work-area has been used ? the sole purpose
2) different types of select query ? only coding examples
note: no links pls
regards,
virus

hi,
Work Area
Description for a data object that is particularly useful when working with internal tables or database tables as a source for changing operations or a target for reading operations.
WORKAREA is a structure that can hold only one record at a time. It is a collection of fields. We use workarea as we cannot directly read from a table. In order to interact with a table we need workarea. When a Select Statement is executed on a table then the first record is read and put into the header of the table and from there put into the header or the workarea(of the same structure as that of the table)of the internal table and then transferred top the body of the internal table or directly displayed from the workarea.
Each row in a table is a record and each column is a field.
While adding or retrieving records to / from internal table we have to keep the record temporarily.
The area where this record is kept is called as work area for the internal table. The area must have the same structure as that of internal table. An internal table consists of a body and an optional header line.
Header line is a implicit work area for the internal table. It depends on how the internal table is declared that the itab will have the header line or not.
.g.
data: begin of itab occurs 10,
ab type c,
cd type i,
end of itab. " this table will have the header line.
data: wa_itab like itab. " explicit work area for itab
data: itab1 like itab occurs 10. " table is without header line.
The header line is a field string with the same structure as a row of the body, but it can only hold a single row.
It is a buffer used to hold each record before it is added or each record as it is retrieved from the internal table. It is the default work area for the internal table.
With header line
SELECT.
Put the curson on that word and press F1 . You can see the whole documentation for select statements.
select statements :
SELECT result
FROM source
INTO|APPENDING target
[[FOR ALL ENTRIES IN itab] WHERE sql_cond]
Effect
SELECT is an Open-SQL-statement for reading data from one or several database tables into data objects.
The select statement reads a result set (whose structure is determined in result ) from the database tables specified in source, and assigns the data from the result set to the data objects specified in target. You can restrict the result set using the WHERE addition. The addition GROUP BY compresses several database rows into a single row of the result set. The addition HAVING restricts the compressed rows. The addition ORDER BY sorts the result set.
The data objects specified in target must match the result set result. This means that the result set is either assigned to the data objects in one step, or by row, or by packets of rows. In the second and third case, the SELECT statement opens a loop, which which must be closed using ENDSELECT. For every loop pass, the SELECT-statement assigns a row or a packet of rows to the data objects specified in target. If the last row was assigned or if the result set is empty, then SELECT branches to ENDSELECT . A database cursor is opened implicitly to process a SELECT-loop, and is closed again when the loop is ended. You can end the loop using the statements from section leave loops.
Up to the INTO resp. APPENDING addition, the entries in the SELECTstatement define which data should be read by the database in which form. This requirement is translated in the database interface for the database system´s programming interface and is then passed to the database system. The data are read in packets by the database and are transported to the application server by the database server. On the application server, the data are transferred to the ABAP program´s data objects in accordance with the data specified in the INTO and APPENDING additions.
System Fields
The SELECT statement sets the values of the system fields sy-subrc and sy-dbcnt.
sy-subrc Relevance
0 The SELECT statement sets sy-subrc to 0 for every pass by value to an ABAP data object. The ENDSELECT statement sets sy-subrc to 0 if at least one row was transferred in the SELECT loop.
4 The SELECT statement sets sy-subrc to 4 if the result set is empty, that is, if no data was found in the database.
8 The SELECT statement sets sy-subrc to 8 if the FOR UPDATE addition is used in result, without the primary key being specified fully after WHERE.
After every value that is transferred to an ABAP data object, the SELECT statement sets sy-dbcnt to the number of rows that were transferred. If the result set is empty, sy-dbcnt is set to 0.
Notes
Outside classes, you do not need to specify the target area with INTO or APPENDING if a single database table or a single view is specified statically after FROM, and a table work area dbtab was declared with the TABLES statement for the corresponding database table or view. In this case, the system supplements the SELECT-statement implicitly with the addition INTO dbtab.
Although the WHERE-condition is optional, you should always specify it for performance reasons, and the result set should not be restricted on the application server.
SELECT-loops can be nested. For performance reasons, you should check whether a join or a sub-query would be more effective.
Within a SELECT-loop you cannot execute any statements that lead to a database commit and consequently cause the corresponding database cursor to close.
SELECT - result
Syntax
... lines columns ... .
Effect
The data in result defines whether the resulting set consists of multiple rows (table-like structure) or a single row ( flat structure). It specifies the columns to be read and defines their names in the resulting set. Note that column names from the database table can be changed. For single columns, aggregate expressions can be used to specify aggregates. Identical rows in the resulting set can be excluded, and individual rows can be protected from parallel changes by another program.
The data in result consists of data for the rows lines and for the columns columns.
SELECT - lines
Syntax
... { SINGLE }
| { { } } ... .
Alternatives:
1. ... SINGLE
2. ... { }
Effect
The data in lines specifies that the resulting set has either multiple lines or a single line.
Alternative 1
... SINGLE
Effect
If SINGLE is specified, the resulting set has a single line. If the remaining additions to the SELECT command select more than one line from the database, the first line that is found is entered into the resulting set. The data objects specified after INTO may not be internal tables, and the APPENDING addition may not be used.
An exclusive lock can be set for this line using the FOR UPDATE addition when a single line is being read with SINGLE. The SELECT command is used in this case only if all primary key fields in logical expressions linked by AND are checked to make sure they are the same in the WHERE condition. Otherwise, the resulting set is empty and sy-subrc is set to 8. If the lock causes a deadlock, an exception occurs. If the FOR UPDATE addition is used, the SELECT command circumvents SAP buffering.
Note
When SINGLE is being specified, the lines to be read should be clearly specified in the WHERE condition, for the sake of efficiency. When the data is read from a database table, the system does this by specifying comparison values for the primary key.
Alternative 2
Effect
If SINGLE is not specified and if columns does not contain only aggregate expressions, the resulting set has multiple lines. All database lines that are selected by the remaining additions of the SELECT command are included in the resulting list. If the ORDER BY addition is not used, the order of the lines in the resulting list is not defined and, if the same SELECT command is executed multiple times, the order may be different each time. A data object specified after INTO can be an internal table and the APPENDING addition can be used. If no internal table is specified after INTO or APPENDING, the SELECT command triggers a loop that has to be closed using ENDSELECT.
If multiple lines are read without SINGLE, the DISTINCT addition can be used to exclude duplicate lines from the resulting list. If DISTINCT is used, the SELECT command circumvents SAP buffering. DISTINCT cannot be used in the following situations:
If a column specified in columns has the type STRING, RAWSTRING, LCHAR or LRAW
If the system tries to access pool or cluster tables and single columns are specified in columns.
Note
When specifying DISTINCT, note that you have to carry out sort operations in the database system for this.
SELECT - columns
Syntax
| { {col1|aggregate( col1 )}
{col2|aggregate( col2 )} ... }
| (column_syntax) ... .
Alternatives:
1. ... *
2. ... {col1|aggregate( col1 )}
{col2|aggregate( col2 )} ...
3. ... (column_syntax)
Effect
The input in columns determines which columns are used to build the resulting set.
Alternative 1
Effect
If * is specified, the resulting set is built based on all columns in the database tables or views specified after FROM, in the order given there. The columns in the resulting set take on the name and data type from the database tables or views. Only one data object can be specified after INTO.
Note
If multiple database tables are specified after FROM, you cannot prevent multiple columns from getting the same name when you specify *.
Alternative 2
... {col1|aggregate( col1 )}
{col2|aggregate( col2 )} ...
Effect
A list of column labels col1 col2 ... is specified in order to build the resulting list from individual columns. An individual column can be specified directly or as an argument of an aggregate function aggregate. The order in which the column labels are specified is up to you and defines the order of the columns in the resulting list. Only if a column of the type LCHAR or LRAW is listed does the corresponding length field also have to be specified directly before it. An individual column can be specified multiple times.
The addition AS can be used to define an alternative column name a1 a2 ... with a maximum of fourteen digits in the resulting set for every column label col1 col2 .... The system uses the alternative column name in the additions INTO|APPENDING CORRESPONDING FIELDS and ORDER BY. .
Column labels
The following column labels are possible:
If only a single database table or a single view is specified after FROM, the column labels in the database table - that is, the names of the components comp1 comp2... - can be specified directly for col1 col2 ... in the structure of the ABAP Dictionary.
If the name of the component occurs in multiple database tables of the FROM addition, but the desired database table or the view dbtab is only specified once after FROM, the names dbtab~comp1 dbtab~comp2 ... have to be specified for col1 col2 .... comp1 comp2 ... are the names of the components in the structure of the ABAP Dictionary.
If the desired database table or view occurs multiple times after FROM, the names tabalias~comp1 tabalias~comp2 ... have to be specified for col1 col2 .... tabalias is the alternative table name of the database table or view defined after FROM, and comp1 comp2 ... are the names of the components in the structure of the ABAP Dictionary.
The data type of a single column in the resulting list is the datatype of the corresponding component in the ABAP Dictionary. The corresponding data object after INTO or APPENDING has to be selected accordingly.
Note
If multiple database tables are specified after FROM, you can use alternative names when specifying single columns to avoid having multiple columns with the same name.
Example
Read specific columns of a single row.
DATA wa TYPE spfli.
SELECT SINGLE carrid connid cityfrom cityto
INTO CORRESPONDING FIELDS OF wa
FROM spfli
WHERE carrid EQ 'LH' AND connid EQ '0400'.
IF sy-subrc EQ 0.
WRITE: / wa-carrid, wa-connid, wa-cityfrom, wa-cityto.
ENDIF.
Alternative 3
... (column_syntax)
Effect
Instead of static data, a data object column_syntax in brackets can be specified, which, when the command is executed, either contains the syntax shown with the static data, or is initial. The data object column_syntax can be a character-type data object or an internal table with a character-type data type. The syntax in column_syntax, like in the ABAP editor, is not case-sensitive. When specifying an internal table, you can distribute the syntax over multiple rows.
If column_syntax is initial when the command is executed, columns is implicitly set to * and all columns are read.
If columns are specificied dynamically without the SINGLE addition, the resulting set is always regarded as having multiple rows.
Notes
Before Release 6.10, you could only specify an internal table with a flat character-type row type for column_syntax with a maximum of 72 characters. Also, before Release 6.10, if you used the DISTINCT addition for dynamic access to pool tables or cluster tables, this was ignored, but since release 6.10, this causes a known exception.
If column_syntax is an internal table with header line, the table body and not the header line is evaluated.
Example
Read out how many flights go to and from a city. The SELECT command is implemented only once in a sub-program. The column data, including aggregate function and the data after GROUP BY, is dynamic. Instead of adding the column data to an internal l_columns table, you could just as easily concatenate it in a character-type l_columns field.
PERFORM my_select USING `CITYFROM`.
ULINE.
PERFORM my_select USING `CITYTO`.
FORM my_select USING l_group TYPE string.
DATA: l_columns TYPE TABLE OF string,
l_container TYPE string,
l_count TYPE i.
APPEND l_group TO l_columns.
APPEND `count( * )` TO l_columns.
SELECT (l_columns)
FROM spfli
INTO (l_container, l_count)
GROUP BY (l_group).
WRITE: / l_count, l_container.
ENDSELECT.
ENDFORM.
SELECT - aggregate
Syntax
... { MAX( col )
| MIN( col )
| AVG( col )
| SUM( col )
| COUNT( DISTINCT col )
| COUNT( * )
| count(*) } ... .
Effect
As many of the specified column labels as you like can be listed in the SELECT command as arguments of the above aggregate expression. In aggregate expressions, a single value is calculated from the values of multiple rows in a column as follows (note that the addition DISTINCT excludes double values from the calculation):
MAX( col ) Determines the maximum value of the value in the column col in the resulting set or in the current group.
MIN( col ) Determines the minimum value of the content of the column col in the resulting set or in the current group.
AVG( col ) Determines the average value of the content of the column col in the resulting set or in the current group. The data type of the column has to be numerical.
SUM( col ) Determines the sum of the content of the column col in the resulting set or in the current group. The data type of the column has to be numerical.
COUNT( DISTINCT col ) Determines the number of different values in the column col in the resulting set or in the current group.
COUNT( * ) (or count(*)) Determines the number of rows in the resulting set or in the current group. No column label is specified in this case.
If you are using aggregate expressions, all column labels that are not listed as an argument of an aggregate function are listed after the addition GROUP BY. The aggregate functions evaluate the content of the groups defined by GROUP BY in the database system and transfer the result to the combined rows of the resulting set.
The data type of aggregate expressions with the function MAX, MIN or SUM is the data type of the corresponding column in the ABAP Dictionary. Aggregate expressions with the function AVG have the data type FLTP, and those with COUNT have the data type INT4. The corresponding data object after INTO or APPENDING has to be selected accordingly.
Note the following points when using aggregate expressions:
If the addition FOR ALL ENTRIES is used in front of WHERE, or if cluster or pool tables are listed after FROM, no other aggregate expressions apart from COUNT( * ) can be used.
Columns of the type STRING or RAWSTRING cannot be used with aggregate functions.
When aggregate expressions are used, the SELECT command makes it unnecessary to use SAP buffering.
Null values are not included in the calculation for the aggregate functions. The result is a null value only if all the rows in the column in question contain the null value.
If only aggregate expressions are used after SELECT, the results set has one row and the addition GROUP BY is not necessary. If a non-table type target area is specified after INTO, the command ENDSELECT cannot be used together with the addition SINGLE. If the aggregate expression count( * ) is not being used, an internal table can be specified after INTO, and the first row of this table is filled.
If aggregate functions are used without GROUP BY being specified at the same time, the resulting set also contains a row if no data is found in the database. If count( * ) is used, the column in question contains the value 0. The columns in the other aggregate functions contain initial values. This row is assigned to the data object specified after INTO, and unless count( * ) is being used exclusively, sy-subrc is set to 0 and sy-dbcnt is set to 1. If count( *) is used exclusively, the addition INTO can be omitted and if no data can be found in the database, sy-subrc is set to 4 and sy-dbcnt is set to 0.
if helpful reward points

Regarding select single and select upto 1 rows

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