[SOLVED] Unique records on a union

[kickstart]

Hi

 

You would hope that it would optimise it, but never certain.

 

Generally understood LIKE to be pretty inefficient and as such something to be used with care.

 

All the best

 

Keith

[fenway]

Generally understood LIKE to be pretty inefficient and as such something to be used with care.

It is -- in the WHERE clause -- but you're already paid that performance penalty.

 

And as mentioned earlier, drop UPPER() unless you've explicitly requested a case-sensitive collation.

[kickstart]

It is -- in the WHERE clause -- but you're already paid that performance penalty.

 

Only if the db recognises that the LIKE clauses are duplicated and doesn't carry them out twice, which is why I wanted to try the "having" so that there was no way for it to do them twice.

 

All the best

 

Keith

[fenway]

Yes, but even if it doesn't, the LIKE clauses in the column list are evaluated on a limited recordset (i.e. the matching rows), so it's neglible.

[kickstart]

Yep, but worth playing with to try out.

 

All the best

 

Keith