A mathematical operator applies a basic arithmetic calculation to the values represented to its left and right:
Parentheses may be used to indicate order of evaluation.
If you omit parentheses, multiplication and dividion take precedence over addition and subtraction, but USoft recommends you ALWAYS write parentheses for readability.
Calculations with non-number values
Mathematical operators are mostly used with number values, where they take their full arithmetic meaning.
On some RDBMSs, you can add days to a date by adding a numerical value, where 1 = a 24-hour day. Likewise, you can use the '-' operator to subtract 2 date values. The result is the time difference, expressed as a number, where 1 = a 24-hour day. USoft recommends that you use functions for date calculations instead.
On MS SQL Server, the '+' operator may be used to concatenate 2 string values. This is RDBMS-specific. USoft recommends you use the equivalent CONCAT function if you can. It has the advantage of being convertible, but the drawback that it takes 2 input values only.