Select single * & Select * upto one row

[Former Member]

What is the difference between Select single * & Select * upto one row?Performance wise which is a better one?

[Former Member]

Hi

have a look at in existing forums you can get answer

with regards

sandhya

[Former Member]

SELECT * UPTO 1 ROW gives better performance..

[Former Member]

Hi,

Difference Between Select Single and Select UpTo One Rows

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 if useful!

[Former Member]

hi

select ... SINGLE [FOR UPDATE]

<b>

If SINGLE is specified, the resulting set has a single line</b>. If the remaining additions to the SELECT command select more than one line from the database, the first line that is found is entered into the resulting set. The data objects specified after INTO may not be internal tables, and the APPENDING addition may not be used.

An exclusive lock can be set for this line using the FOR UPDATE addition when a single line is being read with SINGLE. The SELECT command is used in this case only if all primary key fields in logical expressions linked by AND are checked to make sure they are the same in the WHERE condition. Otherwise, the resulting set is empty and sy-subrc is set to 8. If the lock causes a deadlock, an exception occurs. If the FOR UPDATE addition is used, the SELECT command circumvents SAP buffering.

<b>select single * upto one row selects only one row from the top...</b>

In the data object dobj, the first subsequence is searched for which contents match those of sub_string. However, uppercase/lowercase lettering is not taken into consideration. The content of the data object dobj will be shifted as far possible left or right - depending on the specification in direction - until the byte or character sequence contained in sub_string is at the position that is at the beginning or end of the data object dobj before the shift.

For sub_string, a byte or character-type data object is expected. Closing blanks in data ojects of fixed length are taken into consideration. If sub_string is an empty string, the position in front of the first character or byte is found. To the left, no shift will take place, and to the right there will be a shift by the entire length of dobj.

hope it clears the doubt

regards

dinesh

[Former Member]

Hi,

Select single * would fetch you the first record from the table where ur clause is met.

Select * upto shall get all the details according to ur clause and then outputs the number of rows according to ur mentioned number of rows.

One more difference is that you can use aggregate functions in Select * upto whereas it is not possible in Select Single *.

Hence Select Single * is more efficient that Select * upto.

<b>

Reward points if this info is of use,</b>

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.

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

Regards

[Former Member]

Hi

Difference Between Select Single and Select UpTo One Rows

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 if helpful

Thanks