[SOLVED] SQLite check if record exists
lazarus / 16-Databases

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Pe3s · 2023-05-31 17:07

Hello, how can I check if a record exists, I want the program to
display information that the record exists.
e.g. The given e-mail address exists!

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paweld · 2023-05-31 20:38

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
SQLQuery1.SQL.Text := 'select name from users where email=:mail';  
SQLQuery1.ParamByName('mail').AsString : 'kontakt@example.com';  
 SQLQuery1.Open;    if not SQLQuery1.IsEmpty then   begin    
ShowMessage('E-mail is exist for user: ' +
SQLQuery1.FieldByName('name').AsString);     SQLQuery1.Close;   end  
else   begin     SQLQuery1.Close;     //Add email to db   end;

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Чебурашка · 2023-06-01 06:42

Quote from: Pe3s on May 31, 2023, 07:07:08 pmHello, how can I check if
a record exists, I want the program to display information that the
record exists.
e.g. The given e-mail address exists!

I normally use sql count function.

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  
q.SQL.Text := 'select count(id) as count_id from table where
string_expr=:string_expr';    q.ParamByName('string_expr').AsString :
'what?';      q.Open();  Exists :=
(q.FieldByName('count_id').AsInteger > 0);      q.Close(); if Exists
then  ShowMessage(Format('Requested string_expr "%s" exist',
['what?']));

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Pe3s · 2023-06-01 06:59

And what would the procedure of adding data look like with checking if
the record exists

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Чебурашка · 2023-06-01 07:15

Quote from: Pe3s on June 01, 2023, 08:59:14 amAnd what would the
procedure of adding data look like with checking if the record exists

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  if Exists
then (*say that exists*)else  // add    q.SQL.Text = 'insert into
table (...) values (:...)'  q.ParamByName('...').As<Type> := v...;  //
.. repeat for each param  q.ExecSQL(); (* surround with try except to
make it rite *)(* maybe say that you did add *)

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Zvoni · 2023-06-01 07:23

Quote from: Pe3s on June 01, 2023, 08:59:14 amAnd what would the
procedure of adding data look like with checking if the record exists
Whatever for?
Declare the EMail-Field as UNIQUE and then just add the record.
If the Value is already there you'll get an exception.

btw: An EMail-Address is also a candidate for a Primary Key

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Чебурашка · 2023-06-01 08:11

Quote from: Zvoni on June 01, 2023, 09:23:23 amDeclare the EMail-Field
as UNIQUE and then just add the record.
If the Value is already there you'll get an exception.

Maybe the OP prefers the schema check existence + insert, instead of
insert + manage duplicate exception. I also do, but is just my
personal preference.

I am from the "exception is when your code does the right thing but
something goes wrong, unpredictably, maybe sometimes yes and sometimes
not" school.

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Zvoni · 2023-06-01 08:29

Huh?
Why is OP asking the same question:
https://forum.lazarus.freepascal.org/index.php/topic,61425.0.html

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Чебурашка · 2023-06-01 08:45

Quote from: Zvoni on June 01, 2023, 10:29:35 amHuh?
Why is OP asking the same question:
https://forum.lazarus.freepascal.org/index.php/topic,61425.0.html

Maybe he wants to increase the post count because his goal to become a
Hero Member asap.
We should think about attributing a significance to all the posts we
do (for example if I post "Thanks for the kind answer", I'd say that
my post should not be counted in my posts count)

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Pe3s · 2023-06-01 14:50

Hello, I wanted to dust off the previous question, but the forum did
not allow because it exceeded 120 days, so I asked again because I
wanted to have a better grade at school at the end of the year about
being a hero - pajamas with the Superman logo are enough 

Thank you very much for all the replies, Regards and have a nice day