MySQL SQL
MySQL NULL Functions
MySQL IFNULL() and COALESCE() Functions
Look at the following “Products” table:
| P_Id | ProductName | UnitPrice | UnitsInStock | UnitsOnOrder |
|---|---|---|---|---|
| 1 | Jarlsberg | 10.45 | 16 | 15 |
| 2 | Mascarpone | 32.56 | 23 | |
| 3 | Gorgonzola | 15.67 | 9 | 20 |
Assume that NULL values may be present in the optional “UnitsOnOrder” column.
Examine the SELECT statement that follows:
SELECT ProductName, UnitPrice * (UnitsInStock + UnitsOnOrder)
FROM Products;
In the example above, if any of the “UnitsOnOrder” values are NULL, the result will be NULL.
MySQL IFNULL() Function
If an expression is NULL, you can return a different result using the MySQL IFNULL() method.
If the value is NULL, the example below returns 0.
SELECT ProductName, UnitPrice * (UnitsInStock + IFNULL(UnitsOnOrder, 0))
FROM Products;
MySQL COALESCE() Function
Or we can use the COALESCE() function, like this:
SELECT ProductName, UnitPrice * (UnitsInStock + COALESCE(UnitsOnOrder, 0))
FROM Products;
