Help required on table maintenance generator

Question

Hi all,
       Would any one tell me what is the difference between one step and two step while creating a table maintenace generator for a table.
one more question is i would like to know which search the following code follows while it is executed.
select single vbeln
from vbak into l_vbeln
where vbeln in s_vbeln.
and
select vbeln
from vbak
into l_vbeln
up to 1 rows
where vbeln in s_vbeln.
please do reply soon for the questions.

Answer 1

Hi
table maintanance Generator is used to manually
input values using transaction sm30
follow below steps
1) go to se11 check table maintanance check box under
attributes tab
2) utilities-table maintanance Generator->
create function group and assign it under
function group input box.
also assign authorization group default &NC& .
3)
select standard recording routine radio in table
table mainitainence generator to move table
contents to quality and production by assigning
it to request.
4) select maintaience type as single step.
5) maintainence screen as system generated numbers
this dialog box appears when you click on create
button
6) save and activate table
http://help.sap.com/saphelp_nw04/helpdata/en/cf/21ed2d446011d189700000e8322d00/content.htm
http://help.sap.com/saphelp_46c/helpdata/en/a7/5133ac407a11d1893b0000e8323c4f/frameset.htm
/message/2831202#2831202 [original link is broken]
One step, two step in Table Maintenance Generator
Single step: Only overview screen is created i.e. the Table Maintenance Program will have only one screen where you can add, delete or edit records.
Two step: Two screens namely the overview screen and Single screen are created. The user can see the key fields in the first screen and can further go on to edit further details.
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.
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Regards
Anji