Question

Say you have the following query:

SELECT * FROM table1 WHERE table1.id IN (1, 2, 3, 4, 5, ..., 999999)

What is a reasonable maximum for the number of items in the IN clause? I’m using Sphinx to generate full-text search results and inserting the IDs into a MySQL query. Is this an acceptable way to do it?

Answer 1

You can also have the IN clause take the results of a query, such as:

SELECT * FROM table1 
WHERE table1.id IN 
    (
   SELECT id from table2
    )

That way, you don’t need to generate a text string with all the possible values.

In mysql, you should be able to put as many values in the IN clause as you want, only constrained by the value of “max_allowed_packet”.

http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html#function_in
http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html#sysvar_max_allowed_packet