查询错误：错误：ER_PARSE_ERROR：您的SQL语法错误;检查对应于你的MySQL手册

Question

我想加入下面的查询两个表。

(SELECT CustomerName, OrderDate,
LAG(OrderDate,1) OVER(ORDER BY OrderDate DESC) as Previous_Order_Date
FROM Table1) as t1
INNER JOIN  (SELECT CustomerName, MAX(OrderDate) as Latest_Order_date
             FROM Table1
             GROUP BY CustomerName) as t2
ON t1.CustomerName = t2.CustomerName AND t1.OrderDate = t2.Latest_Order_date

但我得到以下错误：

查询错误：错误：ER_PARSE_ERROR：您的SQL语法错误;检查对应于你的MySQL服务器版本使用附近的正确语法手册“为T1 INNER JOIN（SELECT客户名称，MAX（订购日期）作为Latest_Order_date”在3线

db-fiddle

Answer 1

您需要添加一个部分，如

SELECT t1.CustomerName, t1.Previous_Order_Date, t2.Latest_Order_date
  FROM

对于作为查询的上述部分：

SELECT t1.CustomerName, t1.Previous_Order_Date, t2.Latest_Order_date
  FROM (SELECT CustomerName,
               OrderDate,
               LAG(OrderDate, 1) OVER(ORDER BY OrderDate DESC) as Previous_Order_Date
          FROM Table1) as t1
 INNER JOIN (SELECT CustomerName, MAX(OrderDate) as Latest_Order_date
               FROM Table1
              GROUP BY CustomerName) as t2
    ON t1.CustomerName = t2.CustomerName
   AND t1.OrderDate = t2.Latest_Order_date

Answer 2

这是因为丢失外SELECT子句：

SELECT
    t1.CustomerName,
    t1.Previous_Order_Date,
    t2.Latest_Order_date
FROM
(
    SELECT CustomerName, OrderDate,
        LAG(OrderDate,1) OVER(ORDER BY OrderDate DESC) AS Previous_Order_Date
    FROM Table1
) AS t1
INNER JOIN
(
    SELECT CustomerName, MAX(OrderDate) AS Latest_Order_date
    FROM Table1
    GROUP BY CustomerName
) AS t2
    ON t1.CustomerName = t2.CustomerName AND t1.OrderDate = t2.Latest_Order_date;

但实际上，你也许可以简化您的查询，甚至不使用任何连接：

SELECT
    t.CustomerName,
    t.Previous_Order_Date,
    t.Latest_Order_date
FROM
(
    SELECT CustomerName, OrderDate,
        LAG(OrderDate,1) OVER(ORDER BY OrderDate DESC) AS Previous_Order_Date,
        MAX(OrderDate) OVER (PARTITION BY CustomerName) AS Latest_Order_date
    FROM Table1
) t
WHERE
    t.Previous_Order_Date = t.Latest_Order_date;

这将是正确的，如果它在你的联接匹配，只有通过记录每一行。

请注意，您目前的语法实际上是有效的MySQL的，如果有什么子查询之间来到了UNION，而不是加入。也就是说，以下是有效的语法：

(SELECT CustomerName, OrderDate FROM Table1)
UNION
(SELECT CustomerName, OrderDate FROM Table1)

Answer 3

你没有一个主要的select语句。

尝试是这样的：

SELECT *
FROM (SELECT CustomerName, OrderDate,
LAG(OrderDate,1) OVER(ORDER BY OrderDate DESC) as Previous_Order_Date
FROM Table1) as t1
INNER JOIN  (SELECT CustomerName, MAX(OrderDate) as Latest_Order_date
             FROM Table1
             GROUP BY CustomerName) as t2
ON t1.CustomerName = t2.CustomerName AND t1.OrderDate = t2.Latest_Order_date

MySQL的选择需要在格式的查询：

SELECT *
FROM table1 AS t1
JOIN table2 AS t2
  ON t1.id = t2.id
JOIN (SELECT id, value FROM table3) as t3
  on t3.id = t2.id
WHERE t3.value IS NOT NULL;