How to select all where the condition is null? - php

Question

I have a php code with a query:
$query = "SELECT * FROM TDdb WHERE status = $status AND occupation =$occupation";
I am sending the values status and occupation with a client application to this php code.
This works when I send both status and occupation. But I want it to return rows if I just send status but not occupation also ( I mean no matter what the occupation is).
does anyone have any suggestions?
I would appreciate any help.
PS: I want to do it without if statement and just but changing the query

Answer 1

Personally I would create a base query and append conditions wherever you have them, like so:
$sql = 'SELECT * FROM TDdb';
$conditions = array();
$args = array();
if ($action) {
$conditions[] = 'status = :status';
$args[':status'] = $status;
}
if ($occupation) {
$conditions[] = 'occupation = :occupation';
$args[':occupation'] = $occupation;
}
if ($conditions) {
$sql .= ' WHERE ' . join(' AND ', $conditions);
}
$stmt = $db->prepare($sql);
$stmt->execute($args);

Answer 2

Looks like you've got a few good options for how to do it in SQL, or how to make the SQL string variable in PHP.
One reason to consider using an 'if' in the PHP code for the database access performance.
When you introduce an 'or' condition like that in SQL, you're not going to get index access. It is much harder for the database to determine what path it should take than for the PHP code because the SQL engine optimizes the query without knowing what the variable will resolve to at execution.
You already know in the PHP which version of the query you really want. This will perform better if you make that choice there.

Answer 3

This will work if you pass an occupation or a NULL value.
SELECT *
FROM TDdb
WHERE status = $status
AND ($occupation IS NULL OR occupation = $occupation)

Answer 4

"SELECT * FROM TDdb WHERE status = '$status' AND (occupation = '$occupation' OR occupation IS NULL)";

Answer 5

Apart from the solution provided by #Tom and #Damien Legros, you may create two query strings one with occupation and one without occupation. Something like:
$query = "SELECT * FROM TDdb WHERE status = $status";
if ($occupation != "") {
/*When you have value for occupation*/
$query .= " AND occupation =$occupation";
}
So in this case, data will be returned if you have only the status field. Secondly, please check if the status and occupation fields in table are varchar then you have to enclose them in single quotes (').

Answer 6

Thanks everyone for help. specially jack.
finally i created my query like this:
$query = 'SELECT * FROM TDdb';
if ($status) {
$query = $query." WHERE status = '".$status."'";
}
if ($occupation) {
$query = $query." AND occupation = '".$occupation."'";
}