Question

这是我的观点，它提供了如上所述的输出：

CREATE
  ALGORITHM=UNDEFINED
  DEFINER=`root`@`localhost`
  SQL SECURITY DEFINER
VIEW new_view AS
  SELECT 'pcount'    AS ind_type,
         SUM(pcount) AS Index_val
  FROM   temp
UNION
  SELECT 'ncount',
         SUM(ncount)
  FROM   temp
;

结果：

+----------+-----------+
| ind_type | Index_val |
+----------+-----------+
| pcount   |        76 |
| ncount   |       434 |
+----------+-----------+

现在我创建了另一个使用pcount

从另一个表中获取ncount和MAX()的密钥

CREATE
  ALGORITHM=UNDEFINED
  DEFINER=`root`@`localhost`
  SQL SECURITY DEFINER
VIEW view_name AS
  SELECT pcount,
         ncount
  FROM   temp
  WHERE  id = (SELECT MAX(id) FROM temp)
;

给出结果：

+--------+--------+
| pcount | ncount |
+--------+--------+
|     56 |     56 |
+--------+--------+

如何将此结果视为上述结果？

按照斯蒂芬的回答结果：

+----------+-----------+
| ind_type | Index_val |
+----------+-----------+
|        0 |         0 |
+----------+-----------+
1 row in set (0.01 sec)

Answer 1

你可以试试这个：

CREATE VIEW test.t1 AS (
    SELECT 
        'pcount' AS type,
        `temp`.`pcount` AS value 
    FROM 
        `temp` 
    WHERE (
        `temp`.`id` = (
                SELECT 
                    MAX(`temp`.`id`) 
                FROM 
                    `temp`
        )
    )
    UNION 
    SELECT 
        'ncount' AS type,
        `temp`.`ncount` AS value 
    FROM 
        `temp` 
    WHERE (
        `temp`.`id` = (
                SELECT 
                    MAX(`temp`.`id`) 
                FROM 
                    `temp`
        )
    )
)

Answer 2

您可以使用由两行组成的虚拟表（根据您要忽略的列数）在第二个示例中取消忽略查询结果。这是它的外观：

SELECT t.ind_type,
       CASE t.ind_type
         WHEN 'pcount' THEN v.pcount
         ELSE               v.ncount
       END AS Index_val
FROM   temp AS v
CROSS
JOIN   (
       SELECT 'pcount' AS ind_type
       UNION ALL
       SELECT 'ncount'
       ) AS t
WHERE  v.id = (SELECT MAX(id) FROM temp)

格式化MySQL中的视图输出

2 个答案: