Update in php empties column where no arg supplied

[mccwd]

Greetings,
I have a script to edit a simple user table, the form consists of a dropdown menu to select which user to edit, a checkbox followed by a username change, the same is true 4 password and permissions.

here is table structure:
id int auto, Pkey, Not null
username varchar
password varchar
perm enum ('user','admin') default = user

everything works fine when the form is completed fully entered, but if i select a user and check only 'change password check box', change the password and hit submit the result is a new password but the username is erased. and viseversa if username is changed

here are the querys in my php script:

if ($_POST[conf_username]!=' ')
						{
						//start update
						$query_edit_user_u= "UPDATE store_admin SET username='$_POST[username]' WHERE id='$_POST[sel_id]'";
						$issue_query_edit_user_u = mysql_query($query_edit_user_u) or die(mysql_error());
						}
						if ($_POST[conf_password]!=' ')
						{
						//start update
						$query_edit_user_p= "UPDATE store_admin SET password='$_POST[password]' WHERE id='$_POST[sel_id]'";
						$issue_query_edit_user_p = mysql_query($query_edit_user_p) or die(mysql_error());
						}
						if ($_POST[conf_perm]!=' ')
						{
						//start update
						$query_edit_user_pr= "UPDATE store_admin SET perm='$_POST[perm]' WHERE id='$_POST[sel_id]'";
						$issue_query_edit_user_pr = mysql_query($query_edit_user_pr) or die(mysql_error());
						}

[sneakyimp]

you run three queries every time. if you don't enter data for all 3 queries, you are going to be updating your table with empty data. seems pretty clear to me.

[Roger_Ramjet]

You should be using isset($_POST['conf_username']) to test for data. If nothing is entered into a text box then nothing is Posted for that var. Now NULL is not equal to an empty string so your IF is true and NULL is inserted into the field. Always test Get and Post vars with isset before testing for validity.

[mccwd]

Thx i changed all validations to use isset() function and it worked perfectly, thx 4 all the help