Question

Hi I have a table with a primary:

PRIMARY KEY(`x`,`y`,`Version`,`Revision`)

On table like:

`x`,`y,`version`,`revision`,`data`

x, y, version and revision all count up from zero.

I am trying to figure out how to return the highest revision and its data for every version, given a specifiy x and y. And what indexes could I make to speed it up?

Answer 1

Try this query –

SELECT t1.* FROM table t1
  JOIN (SELECT Version, MAX(Revision) Revision FROM table GROUP BY Version) t2
    ON t1.Version = t2.Version AND t1.Revision = t2.Revision

…to speed up the query you may add indexes on Version and Revision fields. Anyway – you should analyze it using EXPAIN SELECT... statement.