problem with the delete sql query.

Question

1.00/5 (1 vote)

See more:

i have three tables in all users,roles,groups

i am trying to delete userid and groupid from the roles table on selecting userid from the user table . can anyone figure out wots the problem in query.

i wrote a query but it is deleting all the records of userid and roleid in the roles table.

The query i am trying is

C#

SqlCommand cmd = new SqlCommand("Delete ROLES SELECT userid FROM users WHERE username= '" + lbldeletename.Text + "'", MAconn);

and the whole code for rowdeleting event in datagridview is

C#

protected void _rowdeleting(object sender, GridViewDeleteEventArgs e)
    {
        GridViewRow row = (GridViewRow)GridView1.Rows[e.RowIndex];
        Label lbldeletename = (Label)row.FindControl("lblusername");
        
        MAconn.Open();
        SqlCommand cmd = new SqlCommand("Delete ROLES SELECT userid FROM users WHERE username= '" + lbldeletename.Text + "'", MAconn);
        cmd.ExecuteNonQuery();
        MAconn.Close();
        bind();

    }

Posted 9-Sep-11 1:34am

codegeekalpha

Add a Solution

4 solutions

Solution 4

To add to Salini's good answer:

Don't concatenate literals to an SQL statement. Instead always use SqlParameter [^]. So your code could look something like:

C#

protected void _rowdeleting(object sender, GridViewDeleteEventArgs e)
    {
        GridViewRow row = (GridViewRow)GridView1.Rows[e.RowIndex];
        Label lbldeletename = (Label)row.FindControl("lblusername");
        
        MAconn.Open();
        SqlCommand cmd = new SqlCommand("DELETE FROM Roles WHERE UserId = (SELECT u.UserId FROM Users u WHERE u.UserName = @UserName", MAconn);
        cmd.Parameters.AddWithValue("@UserName", lbldeletename.Text);
        cmd.ExecuteNonQuery();
        MAconn.Close();
        bind();
 
    }

This would protect you better from SqlInjections and also prevent from datatype related problems.

Posted 9-Sep-11 3:30am

Wendelius

Solution 2

your query for deltion is incorrect. See
http://www.techonthenet.com/sql/delete.php[^] or
http://msdn.microsoft.com/en-us/library/ms189835.aspx[^]
for more information

Posted 9-Sep-11 1:42am

Herman<T>.Instance

Solution 1

Wrong query gets unexpected result.
Check the syntax. http://msdn.microsoft.com/en-us/library/ms189835.aspx[^]

Posted 9-Sep-11 1:40am

Prerak Patel

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

P.Salini · Accepted Answer · 2011-09-09T01:48:00

Solution 3

The query must be as follows

SQL

"Delete FROM ROLES WHERE userid = ( SELECT userid FROM users WHERE username= '" + lbldeletename.Text + "')"

i think this may help you.

Posted 9-Sep-11 1:48am

P.Salini

Updated 13-Sep-11 0:47am

v2

Comments

Wendelius 9-Sep-11 9:30am

Good answer, my 5