How to Calculate Fields in SQL
A select statement in SQL usually displays column data on a report. At times, however, you might want to display a calculated field on the output. A calculated field is a field whose value is derived from column data.
To learn how calculate fields in a SQL select statement, follow these steps:
- You'll need to setup the MySQL database tables. The instructions for the setup can be found in How to add comments in simple SQL selects. Follow steps 1 through 7 before proceeding to the next step.
- We turn our attention to creating a calculated field.
- Let us presuppose that Census Bureau statistics estimate an 8% population growth in cities in Florida. We wish to display the city name, current
population, estimated population growth and the projected total population. Execute the following statement:
The select statement selects the current population, a calculated field in which the population is multiplied by .08 (8 percent) and then a calculated field that contains the projected total population. The calculations are performed using familiar arithmetic operators such as the
+sign (add) and the
*sign (multiplication). I use the
askeyword to give the calculated fields meaningful column headings.