Use of ParamByName with TQuery 3

[luistsousa]

Hello

I have a very simple question to make (I think). I want create a new field in a mysql table.
I use a mysql database and when i run the code below appear a error message with "general sql error [Mysql].....:

Who can I solve the problem?


Query1.Close();
Query1.SQL.Clear();
Query1.SQL.Add("ALTER TABLE alter_exp, ADD :name CHAR(25)"
Query1.Params.ParamByName("name&quot.AsString := "Deg";
Query1.ExecSQL();


Many thanks
Luis

 

[BillDoorNZ]

have you tried running the query without using parameters?
i.e.

Query1.Close();
Query1.SQL.Clear();
Query1.SQL.Add('ALTER TABLE alter_exp, ADD Deg CHAR(25)');
Query1.ExecSQL();

Does it still fail? Just want to acertain if it is the bind param that is causing the problem. If not, you could always use the format function each time to build the sql statement:

Query1.SQL.Add(Format('ALTER TABLE alter_exp, ADD %s CHAR(25)', ['Deg']));

Any more info on the exception you are getting? as opposed to: "general sql error [Mysql].....:" - care to post the entire exception message?

 

[Svanhooft]

hi

The parameter cann't be used in this sort of ways. A better way is to use a format:


Function AddFieldToDatabase(const sTable, sField: string);
const
CQuery = "ALTER TABLE %s ADD %s CHAR(25)";
var
s: string;
begin
s := Format(CQuery, [sTable, sField]);

Query1.Close();
Query1.SQL.Clear();
Query1.SQL.Add(s);
Query1.ExecSQL();

end;

This function will add char fields of length 25 to a database. It is also possible to give the fieldtype and the length as a parameter.


Function AddFieldToDatabase(const sTable, sField, sType: string);
const
CQuery = "ALTER TABLE %s ADD %s %s";
var
s: string;
begin
s := Format(CQuery, [sTable, sField, sType]);

Query1.Close();
Query1.SQL.Clear();
Query1.SQL.Add(s);
Query1.ExecSQL();

end;

In another function you could use:

AddFieldToDatabase('alter_exp', 'Deg' , 'CHAR(25)');


Steph [Bigglasses]

 

[luistsousa]

Hi

I used the format option and works very well.

Many thanks
Luis