diff .single * &upto 1 row ?
What is the difference between the .....Select Single *
and Select upto 1 row
NAVEEN KUMAR GUDURI replied
Let me give you example
SELECT SINGLE * "Where name = 'AAA '.
Immediately it will search when serch condition is true it will display the data and stops further searching.
So, O/p = 1 , AAA
upto 1 row. "Where name = 'AAA '.
It will fetch all the that are matched with name 'AAA'.
And then display the first row.
(Something like this
So, performance wise when more number of records exists with same conditions it is better to use select single *
But we use this queries depending on the requirment.
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.