1、創建分組 group by

SELECT vend_id, COUNT(*) AS num_prods FROM products
GROUP BY vend_id;

在where字句之後，在order by字句之前。

2、過濾分組

HAVING 過濾分組，where過濾行

SELECT cust_id,COUNT(*) AS orders1 FROM orders
GROUP BY cust_id
HAVING COUNT(*) >=2;

它列出具有兩個以上產品且其價格大於等於4的供應商：

SELECT vend_id,COUNT(*) AS num_prods FROM products
WHERE prod_price >=4
GROUP BY vend_id
HAVING COUNT(*) >=2;

SELECT子句順序

mysql之分組