第11课 使用子查询

• 11.1 子查询
• 11.2 利用子查询进行过滤
  • SELECT order_num
  • FROM OrderItems
  • WHERE prod_id = 'RGAN01';
  • -----------------------------
  • SELECT cust_id
  • FROM Orders
  • WHERE order_num IN (20007,20008);
• 11.3 作为计算字段使用子查询
  • SELECT COUNT(*) AS orders
  • FROM Orders
  • WHERE cust_id = '1000000001';
• 11.4 小结

来自为知笔记(Wiz)