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Multiple DB filtering

Posted on 2002-04-14
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Last Modified: 2010-04-04
I use next code to filter my table :

table1.filter := 'GRUPA= ''A05AA02'' or GRUPA= ''A06AD11'' or GRUPA= ''A07AA11'' or GRUPA= ''C03AA03'' or GRUPA= ''C03CA01'' or GRUPA= ''C03DA01'' or GRUPA= ''C07AA05'' or GRUPA= ''H02AB04'' or GRUPA= ''J01CA01'' or GRUPA= ''J01MA02'' or GRUPA= ''J01MA06'' or GRUPA= ''J05AF05'' or GRUPA= ''L04AX01'' or GRUPA= ''V03AC01'' or GRUPA= ''H02AB07''';

table1.filtered := true;

The problem is that my string is longer than 256 characters and I get an error message when compile the project.

Any suggestion how can I step over this problem?
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Comment
Question by:ginsonic
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13 Comments
 
LVL 3

Accepted Solution

by:
marcoszorrilla earned 400 total points
ID: 6940469
Split the string
you must load for example S1 with 250 characters for example and S2 with the rest

Var
S1,S2:String

Table1.filter:=S1+S2
Table1.Filtered:=True;

Best regards.
Marcos.
0
 
LVL 15

Expert Comment

by:simonet
ID: 6940857
Try this:

table1.filter := '( GRUPA IN (''A05AA02'', ''A06AD11'', ''A07AA11'', ''C03AA03'' , ''C03CA01'', ''C03DA01'', ''C07AA05'', ''H02AB04'', ''J01CA01'', ''J01MA02'', ''J01MA06'', ''J05AF05'', ''L04AX01'', ''V03AC01'', ''H02AB07''))';

table1.filtered := true;



if the code above works it will not only sole the large string problem, but the filtering will also be faster.

Yours,

Alex
0
 
LVL 10

Expert Comment

by:Jacco
ID: 6941212
It also works when splitting up the string in your code without the use of variables:

Table1.Filter := 'first part < 255 charachters' +
  'second part < 255 charachters' +
  'third part < 255 charachters' +
  'etc...';

Regards Jacco
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LVL 10

Expert Comment

by:Jacco
ID: 6941213
With complex filters that change often it might also be better to use the OnFilterRecord event.

Regards Jacco
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 6941260
i would use a tquery instead a ttable,
if there are such complex (where) clauses
affected

meikl ;-)
0
 
LVL 9

Author Comment

by:ginsonic
ID: 6941802
kretzschmar can you tell me more ? Untill now I have used just table+dataSource+DBGrid in my projects :(

I wish to say that I have couple situations when I use ~50 conditions for filtering .
0
 
LVL 9

Author Comment

by:ginsonic
ID: 6941835
simonet , your suggestion get me an error message alike 'Operation not applicable' for this.
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 6941895
guessing simonets suggestion
is not supported by your database :-(

you can do the same as the ttable with a tquery+tdatasource+tdbgrid+tupdatesql (as updateobject of the tquery, if editing, deletes and inserts may possible)

lets say we have a sql-statement like

select * from atable

this shows all entries of atable

if you want to filter, you modify the sql-statement like
select * from atable where condition

you can do this on the fly like

function get_filter_sql(atable, awhereclause : String)
const
  sqltextnowhere := 'select * from atable %s';
  sqltextwhere := sqltextnowhere+' where %s';
begin
  if awhereclause = '' then
   result := format(sqltextnowhere,[atable])
  else
   result := format(sqltextwhere,[atable,awhereclause])
end;

usage sample

query1.close;
query1.sql.text := get_filter_sql(yourtable,yourfilter);
query1.open;

hope this helps

meikl ;-)
0
 
LVL 9

Author Comment

by:ginsonic
ID: 6942407
Look a little more complicated . What's the difference between my filtering and the query's one ?
What gain using a query ?
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 6942506
usual on sql-databases it is recommended to work with queries
-lower overhead
-faster results
-you can order the result by any field(s) with an order by clause

there should be no difference
in the result of the query
and the filtering

in your case, you use dbase,
i guess from previous q's,
it is a workaround

meikl ;-)
0
 
LVL 4

Expert Comment

by:nestorua
ID: 6942918
HI, ginsonic,
If you don't want to use TQuery component and use TTable one
for your purpose it would be reasonable to use OnFilterRecord
event.
Create TStringList, fill it with your specific strings
('A05AA02', ...) and write the following
Accept:=StringListName.IndexOf(GRUPA.AsString)<>-1.
That's all.
Sincerely,
Nestorua.
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 6943067
yep, this may also a solution, Nestorua
0
 
LVL 9

Author Comment

by:ginsonic
ID: 6955969
I choice a different way to step over my problem ( not proposed here ) but this is the first working solution .

Thanks to all experts,

Nick aka ginsonic
0

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