Hi,
...
> 1. COUNT(*) Is there anything wrong with using
> SELECT COUNT(*)
> FROM bleah
> or should I be using
> SELECT COUNT(someField)
> FROM bleah
COUNT(*) might be faster. Its possible that it reads the count from internal
table while COUNT(someField) needs to make a real query. *I think* there
exist a difference how NULLs are treated (included in count or not). That is
if a row has NULL value in "someField" it might not be included in count.
...
> 2. Is two queries a lot less efficient than one?
Usually yes. But with joins (at least in your example), no. The join(-query)
will create a huge temporary table, from which you only select a few rows.
// Jarmo
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