Question

I need to select data from one table and insert it into another table. Currently the SQL looks something like this:

   INSERT INTO A (x, y, z)
   SELECT x, y, z
   FROM B b
   WHERE ...

However, the SELECT is huge, resulting in over 2 millions rows and we think it is taking up too much memory. Informix, the db in this case, runs out of virtual memory when the query is run.

How would I go about selecting and inserting a set of rows (say 2000)? Given that I don’t think there are any row ids etc.

Answer 1

You can do SELECT FIRST n * from Table. Where n is the amount of rows you want, say 2000. Also, in the WHERE clause do an embedded select that checks the table you are inserting in to for rows already existing. So that the next time the statement is ran, it will not include already inserted data.