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C # tutorial
Look at the following "Products" table
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 |
Suppose that the "UnitsOnOrder" column is optional, and may contain NULL values.
Look at the following SELECT statement:
SELECT ProductName, UnitPrice * (UnitsInStock + UnitsOnOrder)
FROM Products;
In the example above, if any of the "UnitsOnOrder" values are NULL, the result will be NULL.
The MySQL IFNULL()
function lets you
return an alternative value if an expression is NULL:
SELECT ProductName, UnitPrice * (UnitsInStock + IFNULL(UnitsOnOrder, 0))
FROM Products;
or we can use the
COALESCE()
function, like this:
SELECT ProductName, UnitPrice * (UnitsInStock + COALESCE(UnitsOnOrder, 0))
FROM Products;
The SQL Server
ISNULL()
function lets
you return an alternative value when an expression is NULL:
SELECT ProductName, UnitPrice * (UnitsInStock + ISNULL(UnitsOnOrder, 0))
FROM Products;
or we can use the COALESCE()
function, like this:
SELECT ProductName, UnitPrice * (UnitsInStock + COALESCE(UnitsOnOrder, 0))
FROM Products;
The MS Access
IsNull()
function returns
TRUE (-1) if the expression is a null value, otherwise FALSE (0):
SELECT ProductName, UnitPrice * (UnitsInStock + IIF(IsNull(UnitsOnOrder), 0, UnitsOnOrder))
FROM Products;
The Oracle NVL()
function achieves the same result:
SELECT ProductName, UnitPrice * (UnitsInStock + NVL(UnitsOnOrder, 0))
FROM Products;
or we can use the COALESCE()
function, like this:
SELECT ProductName, UnitPrice * (UnitsInStock + COALESCE(UnitsOnOrder, 0))
FROM Products;