Difference between select single and select...up to 1 rows

[Former Member]

Hello experts,

I have a little doubt about two select examples that ive seen in a program and i really cant tell the difference betwee them.

The fist one is: Select Single ....

Into .....

From .....

Where .....

And the other one is: Select Single ....

Into .....

From ..... Up to 1 rows

Where .....

Would these two selects retrieve the same information? Are they the same?

Thanx in advance,

Roberto.

[Former Member]

Hello experts,

I have a little doubt about two select examples that ive seen in a program and i really cant tell the difference betwee them.

The fist one is: Select Single ....

Into .....

From .....

Where .....

And the other one is: Select Single ....

Into .....

From ..... Up to 1 rows

Where .....

Would these two selects retrieve the same information? Are they the same?

Thanx in advance,

Roberto.

[Former Member]

HI,

Yes they will get the same information..

Thanks

mahesh

[Former Member]

Those two would do the same...Althought the second is a bit redundant....

Select Single ....
Into .....
From .....Up to 1 rows
Where .....

If you are using SELECT SINGLE your going to always retrieve one row...So you don't need the Up to 1 rows...

Greetings,

Blag.

[Former Member]

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 or lack of, applies any aggregate, ordering or grouping functions to them and then returns the first record of the resultant result set.

or

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.

[former_member189059]

Hello Roberto,

Logically, they do the same thing, but performance wise there can be a difference

This thread will give you all the information you need

/thread/512224 [original link is broken]

[Former Member]

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 or lack of, applies any aggregate, ordering or grouping functions to them and then returns the first record of the resultant result set.

[Former Member]

select up to is faster than select single

it provides better performance

[Former Member]

hi

when select single is used we have to give all primary key fields in where clause which is mandatory.

when using select upto 1 row there is no mandatory condition to give all primary key fields in where clause

[Former Member]

hi,

Hope you got many answers to this. Ok. 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.

Does this answer ur qtn.

Regards

Subbu