MySQL optimized sentence

Question

I have a simple table where I have to extract some records. The problem is that the evaluation function is a very time-consuming stored procedure so I shouldn't to call it twice like in this sentence:

SELECT *, slow_sp(row) FROM table WHERE slow_sp(row)>0 ORDER BY dist DESC LIMIT 10

First I thought in optimize like this:

SELECT *, slow_sp(row) AS value FROM table WHERE value>0 ORDER BY dist DESC LIMIT 10

But it doesn't works due "value" is not processed when the WHERE clause is evaluated.

Any idea to optimize this sentence? Thanks.

Answer 1

What does slow_sp do? To begin optimizing the query you should add an index on dist.

To make your second query work, use HAVING instead of WHERE.