- 10.1 数据分组
- SELECT COUNT(*) AS num_prods
- FROM products
- WHERE vend_id = 'DLL01';
- 10.2 创建分组
- SELECT vend_id, COUNT(*) AS num_prods
- FROM products
- GROUP BY vend_id;
- 10.3 过滤分组
- /*SELECT cust_id, COUNT(*) AS orders
- FROM orders
- GROUP BY cust_id
- HAVING COUNT(*) >= 2;*/
- -----------------------------------------------
- SELECT vend_id, COUNT(*) AS num_prods
- FROM products
- WHERE prod_price >= 4
- GROUP BY vend_id
- HAVING COUNT(*) >= 2;
- 10.4 分组和排序
- SELECT order_num, COUNT(*) AS items
- FROM orderitems
- GROUP BY order_num
- HAVING COUNT(*) >= 3;
- ORDER BY items, order_num;
- 10.5 SELECT子句顺序
- SELECT/FROM/WHERE/GROUP BY/HAVING/ORDER BY
- 10.6 小结
