How can I find out if a table
lazarus / 16-Databases

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Kalevi · 2022-11-03 09:55

How can I find out if a table (table name) is already ready in the
database when I start the node?Using SQLite Database and 
TSQLite3Connection  TSQLTransaction;

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KodeZwerg · 2022-11-03 10:35

With a simple SQL query like:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i SELECT name
FROM sqlite_master WHERE type='table' AND name='table_name_to_look'If
the count = 0 than table does not exists.

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wp · 2022-11-03 11:11

Every descendant of TSQLConnection - TSqlite3Connection is one - has a
method GetTableNames which exports the names of the existing tables
into a TStrings (e.g. TStringList): https://www.freepascal.org/docs-
html/fcl/sqldb/tsqlconnection.gettablenames.html

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Kalevi · 2022-11-03 12:09

I did this procedure, but it doesn't work !
function LookTableName(tablename: String): Boolean;
var   lista: TStringList;
      I: Integer;
begin
  Result := False;
  lista := TStringList.Create;
   SQLite3Connection1.GetFieldNames(tablename,Lista);

  I := 0;
  while (not Result) and (I < lista.Count) do begin
     Result := tablename = lista;
     Inc(I);
     end;
  lista.Free;
end;

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wp · 2022-11-03 12:51

Try this:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
LookTableName(tablename: String): Boolean;var  lista:
TStringList;begin  Result := False;  lista := TStringList.Create; 
try    SQLite3Connection1.GetFieldNames(tablename,Lista);    Result :=
lista.IndexOf(tablename) > -1;  finally    lista.Free;  end;end;

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Kalevi · 2022-11-03 13:14

Kiitos wp , mutta en saanut tuotakaan toimimaan !
The program is running normally, but I would like to add one table to
the database, and for this purpose I want to check if the table has
been added.There's a datamodule in the program that connects to the
database and I've tried that function since the connection to the
database exists.

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Kalevi · 2022-11-03 13:15

Sorry for Finnish
Thanks for the wp, but I couldn't make that work either.

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Zvoni · 2022-11-03 13:16

In Germany, we have a "fun" Game. It's called "spot the Mistake"

Quote from: wp on November 03, 2022, 12:11:19 pmEvery descendant of
TSQLConnection - TSqlite3Connection is one - has a method
GetTableNames which exports the names of the existing tables into a
TStrings (e.g. TStringList): https://www.freepascal.org/docs-
html/fcl/sqldb/tsqlconnection.gettablenames.html


    function LookTableName(tablename: String): Boolean;
    var
      lista: TStringList;
    begin
      Result := False;
      lista := TStringList.Create;
      try
        SQLite3Connection1.GetFieldNames(tablename,Lista);
        Result := lista.IndexOf(tablename) > -1;
      finally
        lista.Free;
      end;
    end;

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Kalevi · 2022-11-03 13:36

Great, I should just get my own code wrong, thank you very much,
Zvoni.Have a nice autumn follow-up for everyone!

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Zvoni · 2022-11-03 17:19

Quote from: Kalevi on November 03, 2022, 02:36:31 pmGreat, I should
just get my own code wrong, thank you very much, Zvoni.Have a nice
autumn follow-up for everyone!
Btw: i just saw that you want to add a table, and check if it exists
beforehand.
Why?
Sqlite supports CREATE TABLE IF NOT EXISTS
If the table exists, nothing happens, if it doesn’t exist it gets
created.
No need to look it up.

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Kalevi · 2022-11-03 17:56

I'm stuffed with patterns and old habits.I've used other databases
like Firebird before.Thank you for the guidance, Zvoni, I tried and
that sentence worked very well, thus simplifying the code.