Returns the first nonnull expression among its arguments.
In this example, a table includes three columns with information about an employee's yearly wage: hourly_wage, salary, and commission. However, an employee receives only one of these pay types.
To determine the total amount paid to all employees, use the COALESCE function to receive only the nonnull value found in the hourly_wage, salary, and commission columns.
SELECT CONVERT(money, COALESCE(null, 5, null, 40 * 52, 65, null)) AS "First nonnull value"