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coalesce is supported in both Oracle and SQL Server and serves essentially the same function as nvl and isnull .
The NULLIF function was introduced in Oracle 9i. It accepts two parameters and returns null if both parameters are equal. If they are not equal, the first parameter value is returned.
Because null represents a lack of data, a null cannot be equal or unequal to any value or to another null. However, Oracle considers two nulls to be equal when evaluating a DECODE function. Please refer to DECODE for syntax and additional information.
ISNULL replaced the Oracle NVL function in the SQL server. When an expression in SQL server is NULL, the ISNULL function allows you to return an alternative value for the null.
coalesce is supported in both Oracle and SQL Server and serves essentially the same function as nvl and isnull. (There are some important differences, coalesce can take an arbitrary number of arguments, and returns the first non-null one. The return type for isnull matches the type of the first argument, that is not true for coalesce, at least on SQL Server.)
Instead of ISNULL(), use NVL().
T-SQL:
SELECT ISNULL(SomeNullableField, 'If null, this value') FROM SomeTable
PL/SQL:
SELECT NVL(SomeNullableField, 'If null, this value') FROM SomeTable
Also use NVL2 as below if you want to return other value from the field_to_check:
NVL2( field_to_check, value_if_NOT_null, value_if_null )
Usage: ORACLE/PLSQL: NVL2 FUNCTION
You can use the condition if x is not null then.... It's not a function. There's also the NVL() function, a good example of usage here: NVL function ref.
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