COUNT is a
set function.COUNT(*)
supplies the total number of values (rows in a result table or group).COUNT(DISTINCT <expression>)
supplies the total number of different values (number of values in the argument of the DISTINCT function).COUNT(ALL <expression>)
supplies the number of values that differ from the NULL value (number of values in the argument of the ALL function)The result has the data type
FIXED(10).Model table:
How many customers are there?
SELECT COUNT (*) number FROM customer
NUMBER |
15 |