Question

使用 MySQL数据库表上的此 SQL 查询，我已经为当前日期和客户选择了应用程序Web上的首次访问：< / p>

mysql> SELECT
    (@cnt := @cnt + 1) AS rowNumber,
    t.myDate,
    t.myCustomer
FROM
    tbl_new AS t
CROSS JOIN (SELECT @cnt := 0) AS dummy
WHERE
    t.myDate IN (CURDATE())
ORDER BY
    t.myDate DESC
LIMIT 1;
+-----------+------------+------------+
| rowNumber | myDate     | myCustomer |
+-----------+------------+------------+
|         1 | 2018-11-12 | 561731A    |
+-----------+------------+------------+
1 row in set

使用 MySQL数据库表上的 SQL 查询，我在网页上选择了当前日期和客户的最后访问权限：

mysql> SELECT
    (@cnt := @cnt + 1) AS rowNumber,
    myDate,
    myCustomer
FROM
    tbl_new
ORDER BY
    myDate DESC
LIMIT 1;
+-----------+------------+------------+
| rowNumber | myDate     | myCustomer |
+-----------+------------+------------+
|         2 | 2018-11-12 | 719020A    |
+-----------+------------+------------+
1 row in set

现在，我需要 UNION ALL 这些SQL查询才能获得唯一的输出，但是最后一次访问的输出是错误的908324A，而不是719020A，

为什么？

mysql> SELECT
    (@cnt := @cnt + 1) AS rowNumber,
    t.myDate,
    t.myCustomer
FROM
    tbl_new AS t
CROSS JOIN (SELECT @cnt := 0) AS dummy
WHERE
    t.myDate IN (CURDATE())
UNION ALL
    SELECT
    (@cnt := @cnt + 1) AS rowNumber,
    myDate,
    myCustomer
FROM
    tbl_new
ORDER BY
    myDate DESC
    LIMIT 2;
+-----------+------------+------------+
| rowNumber | myData     | myCustomer |
+-----------+------------+------------+
|    246616 | 2018-11-12 | 561731A    |
|    111872 | 2018-11-12 | 908324A    |
+-----------+------------+------------+
2 rows in set

Answer 1

我想说你的sql应该是这样的：

SELECT
    (@cnt := @cnt + 1) AS rowNumber,
    t.myDate,
    t.myCustomer
FROM
    tbl_new AS t
CROSS JOIN (SELECT @cnt := 0) AS dummy
WHERE
    t.myDate IN (CURDATE())
ORDER BY
    t.myDate DESC
LIMIT 1
UNION ALL
SELECT
    (@cnt := @cnt + 1) AS rowNumber,
    myDate,
    myCustomer
FROM
    tbl_new
ORDER BY
    myDate DESC
LIMIT 1

使用UNON ALL只需两个句子。

已编辑

我无法发表评论。也许您可以尝试将查询放在括号中：

SELECT * FROM (
SELECT (@cnt := @cnt + 1) AS rowNumber,
...
ORDER BY ...
)
UNION ALL
SELECT * FROM ( ... )

不确定，是否可以提供小提琴...

MySQL数据库表中的第一行和最后一行，用于显示日期和客户

1 个答案: