MySQL の集計関数

SELECT AGGREGATE_FUNCTION(COLUMN_NAME)
FROM TABLE_NAME;

SELECT COUNT(*) AS films FROM film;

+-------+
| films |
+-------+
|  1000 |
+-------+
1 row in set (0.00 sec)

SELECT MIN(length) AS shortest, MAX(length) AS longest, AVG(length) AS mean
FROM film;

+----------+---------+----------+
| shortest | longest | mean     |
+----------+---------+----------+
|       46 |     185 | 115.2720 |
+----------+---------+----------+
1 row in set (0.00 sec)

SELECT SUM(amount) AS takings, COUNT(*) AS payments FROM payment;

+----------+----------+
| takings  | payments |
+----------+----------+
| 67406.56 |    16044 |
+----------+----------+
1 row in set (0.00 sec)

SELECT COUNT(*) AS rows_total, COUNT(address2) AS with_a_value
FROM address;

+------------+--------------+
| rows_total | with_a_value |
+------------+--------------+
|        603 |          599 |
+------------+--------------+
1 row in set (0.00 sec)

SELECT COUNT(*) AS films,
       COUNT(original_language_id) AS with_a_value,
       AVG(original_language_id) AS mean
FROM film;

+-------+--------------+------+
| films | with_a_value | mean |
+-------+--------------+------+
|  1000 |            0 | NULL |
+-------+--------------+------+
1 row in set (0.00 sec)