Question

I have a sequence used to seed my (Integer based) primary keys in an oracle table.

It appears this sequence has not always been used to insert new values into the table. How do I get the sequence back in step with the actual values in the table?

Answer 1

If ID is the name of your PK column and PK_SEQ is the name of your sequence:

1. Find the value of the highest PK by
   SELECT MAX(ID) FROM tableName

2. Find the value of the next PK_SEQ by
   SELECT PK_SEQ.NEXTVAL FROM DUAL

3. If #2 > #1 then nothing needs to be
   done, assuming you treat these
   values as true surrogate keys
4. Otherwise, alter the sequence to
   jump to the max ID by ALTER SEQUENCE
   PK_SEQ INCREMENT BY [#1 value – #2
   value]

5. Bump the sequence by SELECT
   PK_SEQ.NEXTVAL FROM DUAL

6. Reset the sequence increment value
   to 1 by ALTER SEQUENCE PK_SEQ
   INCREMENT BY 1

This all assumes that you don’t have new inserts into the table while you’re doing this…