SQL - 使联接查询更快

Question

I've made a query that selects 2 values from 2 tables. I need to run this query about 32 times when a visitor visits my website. This makes the page quite slow (it takes over 5 seconds to fully load).

The query looks like this:

SELECT tmdb.name, patch.sfo_title
FROM tmdb
RIGHT JOIN patch
ON tmdb.titleid = CONCAT(patch.cusa, '_00')
WHERE cusa = :titleid
LIMIT 1

is there any way to make this query faster? The query isn't the biggest operation if I look at it, so I'm not really sure why it's so slow?

Answer 1

I would write the query as a left join (out of preference, not performance):

SELECT t.name, p.sfo_title
FROM patch p LEFT JOIN
     tmdb t
     ON t.titleid = CONCAT(p.cusa, '_00')
WHERE p.cusa = :titleid
LIMIT 1;

Then for performance, I would recommend indexes on patch(cusa, sfo_title) and t(titleid) .

Note that the use of LIMIT without ORDER BY is suspicious, although you might have reasons for it.

Answer 2

You are joining two tables based on a CALCULATED field? No wonder it is slow. I have no idea how your tables get maintained, but you need to get that concat'ed value of CUSA into the data base as a separate field and get it indexed, as Gordon Linoff suggested. You could even maintain it through On Insert and On Update triggers. Personally, I would examine why you have similar but different keys in your two tables and try to rationalize it down to one. That Concat(CUSA, '_00' ) looks suspiciously like an opportunity to simplify the application.