Why using IN(…) when selecting on indexed fields, will kill the performance of SELECT query?

Question

Avoid using IN(...) when selecting on indexed fields, It will kill the performance of SELECT query.

I found this here: https://wikis.ora

Answer 1

I believe IN is treated the same as a group of ORs, so using ORs won't help.

An alternative is to create a temporary table to hold the values of your IN-clause and then join with that temporary table in your SELECT.

For example:

CREATE TEMPORARY TABLE temp_table (v VARCHAR)

INSERT INTO temp_table  VALUES ('foo')
INSERT INTO temp_table  VALUES ('bar')

SELECT * FROM temp_table tmp, orig_table orig
WHERE temp_table.v = orig.value

DROP TEMPORARY TABLE temp_table