MySQL:连接表的别名 - 故障排除

Question

我在这里有一个关于 SQL fiddle 的工作示例: http://sqlfiddle.com/#!2/e75d6/34

使用以下查询:

SELECT *
FROM (Orders JOIN 
     Salesperson ON 
     Salesperson.ID = Orders.salesperson_id) 
      JOIN 
     (SELECT salesperson_id AS sid, MAX( Amount ) AS MaxOrder
      FROM Orders
      GROUP BY salesperson_id) AS TopOrderAmountsPerSalesperson
     ON (TopOrderAmountsPerSalesperson.sid=Orders.salesperson_id AND
         TopOrderAmountsPerSalesperson.MaxOrder=Orders.Amount) 

但是当我尝试为第一个连接表分配别名时，如下所示:

SELECT *
FROM (Orders JOIN 
     Salesperson ON 
     Salesperson.ID = Orders.salesperson_id) AS SalesOrders
      JOIN 
     (SELECT salesperson_id AS sid, MAX( Amount ) AS MaxOrder
      FROM Orders
      GROUP BY salesperson_id) AS TopOrderAmountsPerSalesperson
     ON (TopOrderAmountsPerSalesperson.sid=SalesOrders.salesperson_id AND
         TopOrderAmountsPerSalesperson.MaxOrder=SalesOrders.Amount) 

我收到语法错误。有什么想法吗？

我使用这个SO作为别名连接表的资源: SQL Alias of joined tables

Answer 1

您可以为整个查询、表名或字段名指定别名，但不能在连接条件上指定别名。尝试以下示例，将 Orders 表的别名设置为 SalesOrders。

SELECT *
FROM Orders AS SalesOrders JOIN 
     Salesperson ON 
     Salesperson.ID = SalesOrders.salesperson_id 
      JOIN 
     (SELECT salesperson_id AS sid, MAX( Amount ) AS MaxOrder
      FROM Orders
      GROUP BY salesperson_id) AS TopOrderAmountsPerSalesperson
     ON (TopOrderAmountsPerSalesperson.sid=SalesOrders.salesperson_id AND
         TopOrderAmountsPerSalesperson.MaxOrder=SalesOrders.Amount) 

检查SQL Fiddle