[Solved] SQL Server Error: The data types nvarchar and nvarchar are incompatible in the subtract operator

HI akhter,

This error The data types nvarchar(max) and nvarchar(max) are incompatible in the subtract operator. throws when you substract two columns with data type as nvarchar.

You can't do a mathematical operation on strings. 

If you want to keep nvarchar datatype, you will have to ensure that all values can be converted to a numeric value.

Use below.

SELECT CAST(IsNULL(Pa.T_Amt, '0') as numeric(18,2)) - CAST(IsNULL(cs.Cs_Amt, '0') as numeric(18,2)) as Received

Example

SELECT CAST(IsNULL('11729.68', '0') as numeric(18,2)) - CAST(IsNULL('11720.68', '0') as numeric(18,2)) as Received

Output

9.00