SQL isnull (Oracle, mysql, mssql)

SQL isnull (oracle, mysql tutorial, mssql)

Isnull
Replace null with the specified replacement value.

Syntax
Isnull (check_expression, replacement_value)

Parameters
Check_expression

Whether the expression is null is checked. Check_expression can be of any type.

Replacement_value

The expression returned when check_expression is null. Replacement_value must be the same

Check_expresssion has the same type.

Return type
Returns the same type as check_expression.

Note
If check_expression is not null, the value of this expression is returned; otherwise

Replacement_value

Example
A. Use isnull With avg
The following example finds the average price of all books and replaces the price column in the titles table with the value $10.00.

All null entries.

Use pubs
Go
Select avg (isnull (price, $10.00 ))
From titles
Go

Next, let's take a look at other database tutorials.

Oracle
Oracle does not have the isnull () function. However, we can use the nvl () function to achieve the same result:

Select productname, unitprice * (unitsinstock + nvl (unitsonorder, 0 ))
From products
Mysql
Mysql also has functions similar to isnull. However, it works with Microsoft's isnull () function.

A little different.

In mysql, we can use the ifnull () function, like this:

Select productname, unitprice * (unitsinstock + ifnull (unitsonorder, 0 ))
From products