SQL聚合函数

SELECT COUNT(shohin_mei) FROM Shohin;--去掉NULL值

SELECT SUM(shiire_tanka) FROM Shohin ;

SELECT MAX(shiire_tanka) FROM Shohin;

SELECT MIN(shiire_tanka) FROM Shohin;

SELECT AVG(shiire_tanka) FROM Shohin;

可以与 DISTINCT 联合使用 

SELECT shohin_bunrui, COUNT(*) FROM Shohin GROUP BY shohin_bunrui;