difference between select single and select upto 1 row.

[Former Member]

Hi

What is the difference between select single and select upto 1 row?

[Former Member]

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.

Refer this for more details

[;

best regards

Sourabh

[ak_upadhyay]

Hi,

SELECT SINGLE returns the first matching row for the given condition and it may not be unique, if there are more matching rows for the given condition.

SELECT ... UP TO 1 ROWS retrieves all the matching records and applies aggregation and ordering and returns the first record.

Inorder to check for the existence of a record then it is better to use SELECT SINGLE than using SELECT ... UP TO 1 ROWS since it uses low memory and has better performance."

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.

Reward points if useful...

Regards

AK

[Former Member]

Hi,

Actually in Select single * only one record is fetched

which ever come across first in data base query , but for

statement select ..upto 1 row , all records are fetched into

a buffer which are satisfied from Where condition in Data

base query , and from buffer first record is fetched .

So Select Single * is better for performance.

rgds,

bharat.

[Former Member]

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.

Reward points..

[Former Member]

Hi,

When you say SELECT SINGLE, it means that you are expecting only one row to be present in the database for the condition you're going to specify in the WHERE clause. so that means, you will have to specify the primary key in your WHERE clause. Otherwise you get a warning.

SELECT UP TO 1 ROWS is used in cases where you just want to make sure that there is at least one entry in the database table which satisfies your WHERE clause. Generally, it is meant to be used for existence-check.

You may not want to really use the values returned by the SELECT statement in this case (thought this may not necessarily be so).And in each case the database optimizer may choose a different strategy to retrieve the data.

Knowing when to use SELECT SINGLE or SELECT ... UP TO 1 ROWS

A lot of people use the SELECT SINGLE statement to check for the existence of a value in a database. Other people prefer to use the 'UP TO 1 ROWS' variant of the SELECT statement.

So what's the difference between using 'SELECT SINGLE' statement as against a 'SELECT .... UP TO 1 ROWS' statement ?

If you're considering the statements

SELECT SINGLE field INTO w_field FROM table.

and

SELECT field INTO w_field FROM table UP TO 1 ROWS. ENDSELECT.

then looking at the result, not much apart from the extra ENDSELECT statement. Look at the run time and memory usage and they may be worlds apart.

Why is this ?? The answer is simple.

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

Go through the below link:

http://www.sap-basis-abap.com/abap/difference-between-select-single-and-up-to-1-row.htm

Regards

Kiran

[Former Member]

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.

Refer this for more details

[;

best regards

Sourabh

[Former Member]

Hi Vighnesh,

"What is the difference between SELECT SINGLE and SELECT ... UP TO 1 ROWS?

SELECT SINGLE returns the first matching row for the given condition and it may not be unique, if there are more matching rows for the given condition.

SELECT ... UP TO 1 ROWS retrieves all the matching records and applies aggregation and ordering and returns the first record.

Inorder to check for the existence of a record then it is better to use SELECT SINGLE than using SELECT ... UP TO 1 ROWS since it uses low memory and has better performance."

Please Reward If helpful.

[Former Member]

Hi,

Select Single * will pickup only one matching record from the database into the buffer, and returns the same to the internal table.

Select upto 1 rows will pickup all the records matching the condition into the buffer, but return the top record to the internal table.

Performance wise select upto 1 row is better than select upto 1 row.

Regards

[Former Member]

Hi,

The difference between select * upto 1 row and select single is that select up to one rows is much quicker that select single as your not really using the all the key fields. Select single is a construct that is designed primarily to read database records with a primary key. If there is no primary key available then at the most it might end up doing a perfunctory sequential search. However in the case of select up to one rows it will assume that there is no primary key and will automatically search for the most appropriate index.

In select * single only a single record is fetched that is whichever one will come first in the data base query. But in the case of select one rows all the records will be fetched and stored in a buffer which pertain to the where condition in the Data base theory.

Regards,

Brown.