MySQL UNION performance vs separate queries
Posted: Fri Aug 28, 2009 12:57 pm
Hi guys
On our intranet system I'm getting counts of related records from various tables... there's 8 record counts I need to get.
There's already 4 other queries on this particular page which get more specific information.
At the moment I'm using UNION to combine all these into a single query then lopping through those results in PHP and setting them to variable variables.
In theory what should give better performance:
8 individual queries from PHP?
Or just a single query with 8 statements joined by UNION?
I would think UNION should give slightly better performance because there'd be less overheard but I'm no expert... there's probably something with UNION that I'm missing.
Cheers, B
On our intranet system I'm getting counts of related records from various tables... there's 8 record counts I need to get.
There's already 4 other queries on this particular page which get more specific information.
At the moment I'm using UNION to combine all these into a single query then lopping through those results in PHP and setting them to variable variables.
In theory what should give better performance:
8 individual queries from PHP?
Or just a single query with 8 statements joined by UNION?
I would think UNION should give slightly better performance because there'd be less overheard but I'm no expert... there's probably something with UNION that I'm missing.
Cheers, B