Not VarIsNull or <> Null
lazarus / 16-Databases

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luca · 2013-07-26 06:46

Hi.
I found e really strange bug. If I test a query field value using
VarIsNull (like if not VarIsNull(Qry1['Field1'])) sometimes I receive
EVariantInvalidOpError.
If I use Qry1['Field1']<>null all it's fine.

So what's best way to check if a query returns null in a field?

Thanks for you great job!

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taazz · 2013-07-26 07:01

Code: [Select]Qry.FieldByName('field1').IsNull

that is the recommended way.

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BigChimp · 2013-07-26 07:28

Quote from: luca on July 26, 2013, 08:46:37 amI found e really strange
bug. If I test a query field value using VarIsNull (like if not
VarIsNull(Qry1['Field1'])) sometimes I receive EVariantInvalidOpError.
If I use Qry1['Field1']<>null all it's fine.
If you have a small FPC demo program that demonstrates this problem,
maybe it has clues for any underlying problems with variant handling
in FPC.

Of course, that depends on the FPC version you're using - please
specify FPC+Lazarus+operating system - you can put it in your forum
signature (see the profile page).