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Author Topic: [SOLVED] query.ChangeCount is always 0  (Read 412 times)

senglit

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[SOLVED] query.ChangeCount is always 0
« on: September 08, 2022, 06:00:26 pm »
hi all,
I got something like this:
Code: Pascal  [Select][+][-]
  1. var
  2.   dbConn: TSQLite3Connection;
  3.   trans: TSQLTransaction;
  4.   query: TSQLQuery;      
  5.  
  6. procedure NewBox(sn:integer;name:string);
  7. var
  8.  cc:integer=0;
  9. begin
  10.     query.Close;
  11.     query.SQL.Text :='insert into box(sn,name) values(' +sn.ToString + ',"' + Name + '")';
  12.     query.ExecSQL;
  13.     cc := query.ChangeCount;
  14.     trans.Commit;
  15.     query.Close;
  16. end;
  17.  

After NewBox is called, with database browser I can see the new record is added into the table "box". But I always got cc as 0. why?

ps: I tried with mysql5.7 and sqlite3, with both of these 2 database type, I always got cc as 0.
« Last Edit: September 09, 2022, 04:38:03 am by senglit »
I use Win10 + Lazarus 2.2.0 + FPC 3.2.2. All 64bit.

JanRoza

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Re: query.ChangeCount is always 0
« Reply #1 on: September 08, 2022, 07:44:30 pm »
Maybe you have to commit first and after that assign the count to cc.
OS: Windows 10 (64 bit) / Linux Mint (64 bit)
Laz: Lazarus 2.2.4 FPC 3.2.2
       CodeTyphon 8.0 FPC 3.3.1

Arioch

  • Sr. Member
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  • Posts: 415
Re: query.ChangeCount is always 0
« Reply #2 on: September 08, 2022, 09:41:40 pm »
I wonder, what would you even expect there. It was always differently named in Delphi

Code: Pascal  [Select][+][-]
  1.     query.ExecSQL;
  2.     cc := query.RowsAffected;
  3.  

See docs - https://docs.getlazarus.org/#fcl+sqldb+tcustomsqlquery.rowsaffected#

And then when the trend became streamlining another pattern emerged:

Code: Pascal  [Select][+][-]
  1.     cc := query.ExecSQL;
  2.  

ChangeCount ? What that even is, from what a library?

Is it perhaps a number of changes that were cached locally and NOT sent to server, something along MIDAS library patterns, like
Code: Pascal  [Select][+][-]
  1. TDataset.Insert;
  2. TDataset.FieldByName('xxx').AsInteger := 10;
  3. TDataset.Post;
  4. cc := TDataset.ChangeCount;
  5. TDataset.ApplyCachedUpdates;
  6.  
« Last Edit: September 08, 2022, 09:44:18 pm by Arioch »

senglit

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Re: query.ChangeCount is always 0
« Reply #3 on: September 09, 2022, 04:37:48 am »
Yes, you are right. I should use RowsAffected instead of ChangeCount. Problem solved. Thank you!

I wonder, what would you even expect there. It was always differently named in Delphi

Code: Pascal  [Select][+][-]
  1.     query.ExecSQL;
  2.     cc := query.RowsAffected;
  3.  

See docs - https://docs.getlazarus.org/#fcl+sqldb+tcustomsqlquery.rowsaffected#

And then when the trend became streamlining another pattern emerged:

Code: Pascal  [Select][+][-]
  1.     cc := query.ExecSQL;
  2.  

ChangeCount ? What that even is, from what a library?

Is it perhaps a number of changes that were cached locally and NOT sent to server, something along MIDAS library patterns, like
Code: Pascal  [Select][+][-]
  1. TDataset.Insert;
  2. TDataset.FieldByName('xxx').AsInteger := 10;
  3. TDataset.Post;
  4. cc := TDataset.ChangeCount;
  5. TDataset.ApplyCachedUpdates;
  6.  
I use Win10 + Lazarus 2.2.0 + FPC 3.2.2. All 64bit.

Zvoni

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  • Posts: 1543
Re: [SOLVED] query.ChangeCount is always 0
« Reply #4 on: September 09, 2022, 12:31:00 pm »
And use Parameters....
Code: Pascal  [Select][+][-]
  1. var
  2.   dbConn: TSQLite3Connection;
  3.   trans: TSQLTransaction;
  4.   query: TSQLQuery;      
  5.  
  6. procedure NewBox(sn:integer;name:string);
  7. var
  8.  cc:integer=0;
  9. begin
  10.     query.Close;
  11.     query.SQL.Text :='insert into box(sn,name) values(:psn,:pname)';
  12.     query.ParamByName('psn').AsInteger:=sn;
  13.     query.ParamByName('pname').AsString:=name;
  14.     query.ExecSQL;
  15.     cc := query.RowsAffected;
  16.     trans.Commit;
  17.     query.Close;
  18. end;
  19.  
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Arioch

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  • Posts: 415
Re: [SOLVED] query.ChangeCount is always 0
« Reply #5 on: September 09, 2022, 05:55:39 pm »
yeah, this too.

One day he can find a hard way that dates and times have different human format with different programs and/or locales, or that NULL and VOID sometimes are not surnames but something different, like one american programmer learnt hard way :-)

https://bobby-tables.com/

 

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