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

silvioprog silvioprog at gmail.com
Fri Aug 30 15:46:47 CEST 2013


2013/8/30 Michael Van Canneyt <michael at freepascal.org>

> 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<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.


hehe... :D

-- 
Silvio Cl├ęcio
My public projects - github.com/silvioprog
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