>Is there any difference in Firebird 1.5 between these 2 queries:
>
>field1 starting with 'Z'
>field1 like 'Z%'
>
>or are they treated exactly the same internally?
>The reason I ask is somebody reckons that like is a lot faster in this
>situation.
>Bear in mind this is Firebird 1.5.

STARTING WITH can generally use indexes. I don't think there's any difference in the two situations you describe (I think Fb 1.5 translates the LIKE into STARTING WITH), but this is only true as long as you use constants. If your situation is slightly different:

Field1 starting with :MyParam
Field1 like :MyParam

then the situation is very different. In such a situation, STARTING WITH can use an index, whereas LIKE cannot (at prepare time, LIKE doesn't know whether the parameter starts with a wildcard character or a fixed value).

So generally, I'd recommend using STARTING WITH rather than LIKE.

Still, in specific situations, LIKE can be quicker. That is, when the optimizer chooses to use the index with STARTING WITH, but where using that particular index actually proves to cause a slowdown. You may have seen other messages on this list where +0 or ||'' is used to avoid a particular index from being used and basically using 'field1 LIKE :MyParam' is identical to 'field1+0 STARTING WITH :MyParam'. Even in this situation would I not recommend using field1 LIKE, since field1+0 STARTING WITH tells me that it is a conscientious choice from the programmer, whereas LIKE might be due to not even considering STARTING WITH.

So, generally use STARTING WITH if you know how the field starts, and LIKE when you're trying to match a particular pattern that is more complex. If you know how the field starts and have a pattern later on in the field, use both STARTING WITH and LIKE if you want an index for the field to be used.

HTH,
Set