Mysql improve SELECT speed

Question

I\'m currently trying to improve the speed of SELECTS for a MySQL table and would appreciate any suggestions on ways to improve it.

We have over 300 million records

Answer 1

Try inserting just the needed dates into a temporary table and the finishing with a select on the temporary table for the tags and ordering.

CREATE temporary table foo
SELECT date, value 
FROM table 
WHERE date BETWEEN 'x' and 'y' ;

ALTER TABLE foo ADD INDEX index( tag );

SELECT date, value 
FROM foo 
WHERE tag = "a" 
ORDER BY date;

if that doesn't work try creating foo off the tag selection instead.

CREATE temporary table foo
SELECT date, value 
FROM table 
WHERE tag = "a";    

ALTER TABLE foo ADD INDEX index( date );

SELECT date, value 
FROM foo 
WHERE date BETWEEN 'x' and 'y' 
ORDER BY date;