Lazarus

Free Pascal => Database => Topic started by: johnmc on January 12, 2020, 03:24:40 pm

Title: Filter syntax
Post by: johnmc on January 12, 2020, 03:24:40 pm

I have been trying to find some documenation regarding the syntax of the filter string used to filter a dataset, hitting F1 brings up only a brief description. Where can I find a complete description?

The best that I can come up with is the wiki https://wiki.lazarus.freepascal.org/Lazarus_Tdbf_Tutorial#Index.2Ffilter_on_strings (https://wiki.lazarus.freepascal.org/Lazarus_Tdbf_Tutorial#Index.2Ffilter_on_strings)

Was there some sort of software specification writen for this if so where would I find it?

Title: Re: Filter syntax
Post by: howardpc on January 12, 2020, 03:30:53 pm

Are you asking specifically about the Lazarus/FPC implementation of TDbf, or some other dataset descendant?

Title: Re: Filter syntax
Post by: johnmc on January 12, 2020, 03:48:45 pm

I am using Sqlite3, so that would be my preference if it makes any difference.

Title: Re: Filter syntax
Post by: balazsszekely on January 12, 2020, 06:35:06 pm

If you're using TSQLQuery, which is a TCustomBufDataset descendent,  the solution is quite simple: create an OnFilterRecord for the Query, then:

Code: Pascal  [Select][+][-]

1. procedure TForm1.SQLQuery1FilterRecord(DataSet: TDataSet; var Accept: Boolean);
2. begin
3.   Accept := SQLQuery1.FieldByName('FIRSTNAME').AsString = 'John';
4. end;
5.  

The code is self explanatory I guess, if not please let us know.

Title: Re: Filter syntax
Post by: johnmc on January 12, 2020, 09:47:19 pm

GetMem I was using TDataSet.Filter and want more info on the format and syntax of the filter string.

Code: Pascal  [Select][+][-]

1.       myFilter := 'Country = ' + QuotedStr(DBGrid1.SelectedField.AsString);
2.       SQLQuery.filter := myFilter;
3.       SQLQuery.Filtered := True;
4.