How to find the next generated value for a auto-increment column?

Solution 1:

Tim, I had faced the same issue where I needed to restart the identity to the next value. I was using db2v9.1.

Unfortunately, there is no way to specify the next value automatically. As per DB2 documentation the value should be a 'numeric constant'. Hence I had to do a select max(id), get the value and replace it in the alter..restart stmt manually.

I don't remember if I tried this - but you can write an sp where max(id) is set in a variable and assign the variable in the alter...restart stmt. (I am unable to try as I dont hav access to any db2 database anymore). I doubt it'll work though. (If it works do let me know :))

DB2 reference:

RESTART or RESTART WITH numeric-constant

Resets the state of the sequence associated with the identity column. If WITH numeric-constant is not specified, the sequence for the identity column is restarted at the value that was specified, either implicitly or explicitly, as the starting value when the identity column was originally created. The column must exist in the specified table (SQLSTATE 42703), and must already be defined with the IDENTITY attribute (SQLSTATE 42837). RESTART does not change the original START WITH value.

The numeric-constant is an exact numeric constant that can be any positive or negative value that could be assigned to this column (SQLSTATE 42815), without non-zero digits existing to the right of the decimal point (SQLSTATE 428FA). The numeric-constant will be used as the next value for the column.

Solution 2:

Can't you use a sequence number in DB2 then use sequence. nextval() ?

Link to automatically generating sequence values in DB2: http://www.ibm.com/developerworks/data/library/techarticle/0302fielding/0302fielding.html

Solution 3:

Your problem maybe solved by now, but for all the others with the same problem: I can offer a solution for getting the max_id +1 for all tables. The only restriction is, that the source column has to be a autoincrement column (GENERATED= 'D'). The resultset can be executed via clp or other query tools.

SELECT   'alter table ' || rtrim(TABSCHEMA) || '.' || TABNAME || ' alter column ' || COLNAME || ' restart with ' || 
cast((case when (trim ((replace ( HIGH2KEY, '+' , '' )))) = '' then 0 else integer(trim ((replace ( HIGH2KEY, '+' , '' ))))+2 end) as varchar(20)) 
|| ' ;'
FROM     SYSCAT.COLUMNS
WHERE    GENERATED = 'D'