In a SQL with LEFT OUTER JOIN I had to sum some columns but some of them returned with NULL value and the result of it was a NULL.
So imagine that we want to add table1`.`columnA`to `table2`.`columnB`, we do something like this
SELECT *, (table1`.`columnA` + `table2`.`columnB`) AS total
and if some of them is NULL the total will be NULL.
What I had to do was this
SELECT *, (ifnull(`table1`.`columnA`,0 ) + ifnull(`table2`.`columnB`, 0)) AS total
And if you want to put it on codeigniter where is how I made it:
$this->db->select('*, (ifnull(`table1`.`columnA`,0 ) + ifnull(`table2`.`columnB`, 0)) AS total', FALSE);
Note the , FALSE, it has to be there.
$this->db->select() accepts an optional second parameter. If you set it to FALSE, CodeIgniter will not try to protect your field or table names with backticks. This is useful if you need a compound select statement.
http://ellislab.com/codeigniter/user-guide/database/active_record.html
