It probably checks the information_schema database which has all of that information. -- Kili.io - OpenStack for Africa: kili.io Musings: twitter.com/varud <https://twitter.com/varud> About Adam: www.linkedin.com/in/adamcnelson On Wed, Oct 23, 2013 at 12:38 PM, Peter Karunyu <pkarunyu@gmail.com> wrote:
Dear MySQL gurus,
So I have this query:
*CREATE TABLE IF NOT EXISTS my_table_a ( SELECT * FROM my_table_b WHERE some_column=some_value);*
My question is, how does MySQL evaluate it? Does it start with the SELECT * then goes to check if that table exists, then creates the table?
The reason I am asking is because the *SELECT * FROM my_table_b WHERE some_column=some_value *part is particularly nasty and takes forever, and therefore, I was thinking of splitting it into two thus:
1. $x = SELECT COUNT(1) FROM information_schema.tables WHERE table_schema='my_db' AND table_name='my_table_a' 2. if ( ! $x ) { CREATE TABLE my_table_a ( SELECT * FROM my_table_b WHERE some_column=some_value); }
And therefore, possibly save a few seconds.
Or am I searching for speed in the wrong place?
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