[fpc-pascal] How to clear the value of a field in a table using parameters?

Michael Van Canneyt michael at freepascal.org
Fri Aug 30 15:45:44 CEST 2013



On Fri, 30 Aug 2013, silvioprog wrote:

> 2013/8/29 Michael Van Canneyt <michael at freepascal.org>
>       On Thu, 29 Aug 2013, silvioprog wrote:
> 
>
>             Other interesting feature is the property EmptyAsNull:
>
>             http://docwiki.embarcadero.com/VCL/XE/en/IBCustomDataSet.TIBStringField.EmptyAsNull
>
>             It tests if field (ftString) is empty (f = ''), if yes, it set the field value to null (f.Clear).
> 
>
>       Apparently a IBX specific extension.
>
>       I don't see the value of this. empty and null are different things.
>
>       Michael.
> 
> 
> Some Delphi components (Zeos, JvDBEdit) have this option.
> 
> Assuming this table:
> 
> test
>   id integer,
>   name varchar(10) not null unique
> 
> You can:
> 
> id|name
> 1| <null>
> 2| <null>
> 
> But:
> 
> 1| <empty>
> 2| <empty> << error, unique key
> 
> I implemented "EmptyAsNull" directly in my project. It is very useful. In my webpages, if the user clear a input, I send a
> null value to the table.

Good for you :)

Michael.


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