Performance problem in select data from data base

Question

hello all,
could you please suggest me which select statement is good for fetch data form data base if data base contain more than 10 lac records.
i am using SELECT PACKAGE SIZE n statement,  but it's taking lot of time .
with best regards
srinivas rathod

Answer 1

Hi Srinivas,
if you have huge data and selecting ,you could decrease little bit time if you use better techniques.
I do not think SELECT PACKAGE SIZE  will give good performance
see the below examples :
ABAP Code Samples for Simple Performance Tuning Techniques
1. Query including select and sorting functionality
tables: mara, mast.
    data: begin of itab_new occurs 0,
             matnr like mara-matnr,
             ernam like mara-ernam,
             mtart like mara-mtart,
             matkl like mara-matkl,
             werks like mast-werks,
           aenam like mast-aenam,
stlal like mast-stlal,
     end of itab_new.
select fmatnr fernam fmtart fmatkl gwerks gaenam g~stlal
into table itab_new from mara as f inner join mast as g on
fmatnr = gmatnr where gstlal = '01' order by fernam.
Code B
tables: mara, mast.
data: begin of itab_new occurs 0,
      matnr like mara-matnr,
      ernam like mara-ernam,
      mtart like mara-mtart,
      matkl like mara-matkl,
      werks like mast-werks,
      aenam like mast-aenam,
      stlal like mast-stlal,
end of itab_new.
select fmatnr fernam fmtart fmatkl gwerks gaenam g~stlal
into table itab_new from mara as f inner join mast as g on f~matnr =
gmatnr where gstlal = '01'.
sort itab_new by ernam.
Both the above codes essentially do the same function, but the execution time for code B is considerably lesser than that of Code A. Reason: The Order by clause associated with a select statement increases the execution time of the statement, so it is profitable to sort the internal table once after selecting the data.
2. Performance Improvement Due to Identical Statements – Execution Plan
Consider the below queries and their levels of efficiencies is saving the execution
tables: mara, mast.
data: begin of itab_new occurs 0,
      matnr like mara-matnr,
      ernam like mara-ernam,
      mtart like mara-mtart,
      matkl like mara-matkl,
      werks like mast-werks,
      aenam like mast-aenam,
      stlal like mast-stlal,
end of itab_new.
select fmatnr fernam fmtart fmatkl gwerks gaenam g~stlal
into table itab_new from mara as f inner join mast as g on f~matnr =
gmatnr where gstlal = '01' .
sort itab_new.
select fmatnr fernam
fmtart fmatkl gwerks gaenam g~stlal
into table itab_new from mara as
f inner join mast as g on f~matnr =
gmatnr where gstlal
= '01' .
Code D (Identical Select Statements)
tables: mara, mast.
data: begin of itab_new occurs 0,
      matnr like mara-matnr,
      ernam like mara-ernam,
      mtart like mara-mtart,
      matkl like mara-matkl,
      werks like mast-werks,
      aenam like mast-aenam,
      stlal like mast-stlal,
end of itab_new.
select fmatnr fernam fmtart fmatkl gwerks gaenam g~stlal
into table itab_new from mara as f inner join mast as g on f~matnr =
gmatnr where gstlal = '01' .
sort itab_new.
select fmatnr fernam fmtart fmatkl gwerks gaenam g~stlal
into table itab_new from mara as f inner join mast as g on f~matnr =
gmatnr where gstlal = '01' .
Both the above codes essentially do the same function, but the execution time for code B is considerably lesser than that of Code A. Reason: Each SQL statement during the process of execution is converted into a series of database operation phases. In the second phase of conversion (Prepare phase) an “execution  plan” is determined for the current SQL statement and it is stored, if in the program any identical select statement is used, then the same execution plan is reused to save time. So retain the structure of the select statement as the same when it is used more than once in the program.
3. Reducing Parse Time Using Aliasing
A statement which does not have a cached execution plan should be parsed before execution; this parsing phase is a highly time and resource consuming, so parsing time for any sql query must include an alias name in it for the following reason.
1.     Providing the alias name will enable the query engine to resolve the tables to which the specified fields belong to.
2.     Providing a short alias name, (a single character alias name) is more efficient that providing a big alias name.
Code E
select jmatnr jernam jmtart jmatkl
gwerks gaenam g~stlal into table itab_new from mara as
j inner join mast as g on jmatnr = gmatnr where
            g~stlal = '01' .
In the above code the alias name used is ‘ j ‘.
4. Performance Tuning Using Order by Clause
If in a SQL query you are going to  read a particular database record based on some key values mentioned in the select statement, then the read query can be very well optimized by ordering the fields in the same order in which we are going to read them in the read query.
Code F
tables: mara, mast.
data: begin of itab_new occurs 0,
      matnr like mara-matnr,
      ernam like mara-ernam,
      mtart like mara-mtart,
      matkl like mara-matkl,
      end of itab_new.
select MATNR ERNAM MTART MATKL from mara into table itab_new where
MTART = 'HAWA' ORDER BY  MATNR ERNAM  MTART MATKL.
read table itab_new with key MATNR = 'PAINT1'   ERNAM = 'RAMANUM'
MTART = 'HAWA'   MATKL = 'OFFICE'.
Code G
tables: mara, mast.
data: begin of itab_new occurs 0,
      matnr like mara-matnr,
      ernam like mara-ernam,
      mtart like mara-mtart,
      matkl like mara-matkl,
      end of itab_new.
select MATNR ERNAM MTART MATKL from mara into table itab_new where
MTART = 'HAWA' ORDER BY  ERNAM MATKL MATNR MTART.
read table itab_new with key MATNR = 'PAINT1'   ERNAM = 'RAMANUM'
MTART = 'HAWA'   MATKL = 'OFFICE'.
In the above code F, the read statement following the select statement is having the order of the keys as MATNR, ERNAM, MTART, MATKL. So it is less time intensive if the internal table is ordered in the same order as that of the keys in the read statement.
5. Performance Tuning Using Binary Search
A very simple but useful method of fine tuning performance of a read statement is using ‘Binary search‘ addition to it. If the internal table consists of more than 20 entries then the traditional linear search method proves to be more time intensive.
Code H
select * from mara into corresponding fields of table intab.
sort intab.     
read table intab with key matnr = '11530' binary search.
Code I
select * from mara into corresponding fields of table intab.
sort intab.     
read table intab with key matnr = '11530'.
Thanks
Seshu