topic Re: select single in Application Development and Automation Discussions

select single

Former Member — Tue, 17 Apr 2007 05:35:02 GMT

Hi what is the difference between select single * and select up to 1 row?

Re: select single

Former Member — Tue, 17 Apr 2007 05:37:15 GMT

chk this

http://www.sap-img.com/abap/difference-between-select-single-and-select-upto-one-rows.htm

Re: select single

Former Member — Tue, 17 Apr 2007 05:39:07 GMT

Hi Balu,

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

You need to mention all the key fields of the table.

No END SELECT required.

More performance compared to upto 1 row.

Where as UP to 1 row.

YOu can use if you do not have all the primiary key fields available.

END SELECT requeired.

Since all keys are not passing, possiblities of have other rows which satisfies the condition.

Select Statement with EndSelect is a loop, which in a single run retrieves a single Record. This Record has to be stored in a Work Area and then appended into an Internal Table.

Select Statements without EndSelect is not a loop and it retrieves the whole Record set matching the Criteria in a single shot and has to be Stored in an Internal Table Directly.

The most important thing to remember about the SELECT SINGLE is

There are several things to remember:

1) It retrieves only one row

2) It does not need an ENDSELECT statement

3) THE FULL KEY OF THE TABLE MUST BE INCLUDED IN

THE WHERE CLAUSE OF THE SELECT STATEMENT

Hope this resolves your query.

Reward all the helpful answers.

Regards

Re: select single

Former Member — Tue, 17 Apr 2007 05:40:28 GMT

Hi Balu,

Select Single fethces the data based upon primary keys. As soon as it gets the required record it stops searching and returns the value to the define WA.

Select upto 1 row fetches all the records that match the condition and keep it at ABAP memory and from there it will get the first record into the defined WA.

So select Single is better in Performance

Regards,

Shafi

Re: select single

Former Member — Tue, 17 Apr 2007 05:41:51 GMT

hi,

select single is used only when all the key fields are specified in the where clause.

i.e according to the given conditions only one record should exist in the db table.

where as select up to 1 rows is used to select only one record satisfying the given conditions.

as per performance select single hits database only once where select up to 1 rows.......endselect hits two times.

Re: select single

Former Member — Tue, 17 Apr 2007 05:42:35 GMT

Hi,

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.

Look for detail at Difference between select single and up to 1 row

Regards

Sudheer

Re: select single

former_member632991 — Tue, 17 Apr 2007 05:44:15 GMT

Hi,

Check this link in sdn

https://www.sdn.sap.com/irj/sdn/wiki?path=/display/home/differencebetweenselectsingleandselectupto.&

Regards,

Sonika

Re: select single

Former Member — Tue, 17 Apr 2007 05:47:25 GMT

Hi,

If you are interested if there exists at least one row of a database

table or view with a certain condition, use the Select ... Up To 1

Rows statement instead of a Select-Endselect-loop with an Exit.

If all primary key fields are supplied in the Where condition you

can even use Select Single.

Select Single requires one communication with the database system,

whereas Select-Endselect needs two.

Regards,

Re: select single

Former Member — Tue, 17 Apr 2007 05:56:28 GMT

Hi,

SELECT SINGLE:

1. Select single is based on PRIMARY KEY

2. It will take the first record directly without searching of all relevant records.(Though you have lot of records for given condition)

SELECT UPTO 1 ROW :

It will check all records for given condition and take the first record .

It means in select single no searching, where as other searching.

Therefore, select single more efficient than UPTO 1 ROW.

Give reward if helpful

Thanks

Vana