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hi all experts

Former Member
0 Kudos

hi

i would like to know the difference between

select single fields where has all primary keys

and

select fields up to 1 rows where has all primary keys

i do not want performance wise difference.

give me really good answers other than performance difference.

thanx

rocky

4 REPLIES 4

Former Member
0 Kudos

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.

Regards,

Bhaskar

Former Member
0 Kudos

Hi dear..

we use upto one rows when we are not sure qbout primary keys in where clause that is we use other fields of table in where clause..

whereas we use select single only when we are sure about PKs and put all PKs in where clause..

regards

sharadendu_agrawal
Active Participant
0 Kudos

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.

Hope it helps !!!

Reward If Helpful...

Cheers,

Sharadendu

Former Member
0 Kudos

hi,

select single gives the first row of the vales that satisfy the given criteria where as while using select upto 1 row may give any one row that satisfies the given criteria.

regards,

srinivas

<b>*reward points, if helpful*</b>