The Cast() function is used to convert a data type variable or data from one data type to another data type.
CAST ( [Expression] AS Datatype)
The data type to which you are casting an expression is the target type. The data type of the expression from which you are casting is the source type.
DECLARE @A varchar(2) DECLARE @B varchar(2) set @A='25a' set @B='15' Select CAST(@A as int) + CAST(@B as int) as Result --'25a' is casted to 25 (string to int) --'15' is casted to 15 (string to int) --Result --40 DECLARE @C varchar(2) = 'a' select CAST(@C as int) as Result --Result --Conversion failed when converting the varchar value 'a' to data type int.
Throws error if failed