Select NULL columns without using "IS NULL"

Question

Hello I need to select all the NULL records in my database which have the column called "cliente_pretenece"

The problem is that I can't define it inside the sql query using IS NULL, because I am using different criteria’s for select, here is the select code:

$sql = "SELECT * FROM users WHERE 1";
if (!empty($id)) {
  $sql .= " AND userID = '$id' ";
}
if (!empty($telefono)) {
  $sql .= " AND telefono LIKE '%$telefono%' ";
}
if (!empty($cliente_pretenece)) {
  $sql .= " AND cliente_pretenece = '$cliente_pretenece' ";
}

the column cliente_pretence will always have 3 different states, and the select code from whch the call is coming is:

<select>
<option  value="SDQ">State 1</option>
<option  value="SA">State 2</option>
<option  value="NULL">Nothing</option>
</select>

So any help will be very welcome. Thanks

Matti Virkkunen · Accepted Answer · 2014-04-16 01:58:14Z

2

You have to use IS NULL. Modify your code so that it reacts differently to the NULL value and generates an IS NULL test instead of a comparison.

Also, learn about parametrized queries before you get an SQL injection.

answered Apr 16, 2014 at 1:58

Matti Virkkunen

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8 Comments

John Siniger Over a year ago

this code is for local use only it is not used in internet.

Matti Virkkunen Over a year ago

That's no excuse to be lazy. Besides what if a user enters a ' character? They'll get an error.

John Siniger Over a year ago

there isn't any <input>'s only select tags so the user don't have an option to write anything. The code is really old and I need a simple modification in other cases I have to revriew the whole system and that goal doesn't fit in the time frame.

Matti Virkkunen Over a year ago

Where does $telefono come from?

John Siniger Over a year ago

<option value="yes">Telefono</option> <option value="no">No Telefono</option>

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