[fpc-pascal] How to clear the value of a field in a table using parameters?

silvioprog silvioprog at gmail.com
Thu Aug 29 18:36:22 CEST 2013


I'm trying to do something with a dataset, but I think that isn't possible.

Assuming I have the following table:

create table users (
id serial not null primary key,
email varchar(100),
 nickname varchar(20) not null

And the following records:

id | email | nickname
1 | user1 at domain.com | user1
2 | user2 at domain.com | user2
3 | user3 at domain.com | user3

I want to clear the email of the second user, but using parameters:

id | email | nickname
1 | user1 at domain.com | user1
2 | <null> | user2
3 | user3 at domain.com | user3

But when I try this:

  SQLQuery1.SQL.Add('update users set email = :email');
  SQLQuery1.SQL.Add('where id = :id');
  SQLQuery1.ParamByName('id').AsInteger := 2;

I got:

"Project project1 raised exception class "EDatabaseError" with message:
PQConnection1: Unknown fieldtype for parameter "email"."

I know that I could solve easily via literal string, but I need to use
parameters anyway.

How I solve this?

Here in Brazil, a friend suggested this:

  VParam := SQLQuery1.ParamByName('email');
  VParam.DataType := ftString;

Is this the only way? '-'

Thank you!

Silvio Cl├ęcio
My public projects - github.com/silvioprog
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