Mysql 从并集运算符中消除空值
我们应该如何消除空值而不是将其保留在单独的行中,值必须驻留在列中,从而通过使用已执行结果集中的联合集运算符使空值消失 考虑一下简单的SQL查询Mysql 从并集运算符中消除空值,mysql,sql,mariadb,union,sql-null,Mysql,Sql,Mariadb,Union,Sql Null,我们应该如何消除空值而不是将其保留在单独的行中,值必须驻留在列中,从而通过使用已执行结果集中的联合集运算符使空值消失 考虑一下简单的SQL查询 SELECT * FROM ( (SELECT 6 + 2 AS addition, NULL AS subtraction, NULL AS multiplication, NULL AS division FROM DUAL) UNION (SELEC
SELECT
*
FROM
(
(SELECT
6 + 2 AS addition,
NULL AS subtraction,
NULL AS multiplication,
NULL AS division
FROM
DUAL)
UNION
(SELECT
NULL AS addition,
6 - 2 AS subtraction,
NULL AS multiplication,
NULL AS division
FROM
DUAL)
UNION
(SELECT
NULL AS addition,
NULL AS subtraction,
6 * 2 AS multiplication,
NULL AS division
FROM
DUAL)
UNION
(SELECT
NULL AS addition,
NULL AS subtraction,
NULL AS multiplication,
6 / 2 AS division
FROM
DUAL)
) A;
实际结果:
+----------+-------------+----------------+----------+
| addition | subtraction | multiplication | division |
+----------+-------------+----------------+----------+
| 8 | NULL | NULL | NULL |
| NULL | 4 | NULL | NULL |
| NULL | NULL | 12 | NULL |
| NULL | NULL | NULL | 3.0000 |
+----------+-------------+----------------+----------+
4 rows in set (0.00 sec)
+----------+-------------+----------------+----------+
| addition | subtraction | multiplication | division |
+----------+-------------+----------------+----------+
| 8 | 4 | 12 | 3.0000 |
+----------+-------------+----------------+----------+
1 row in set (0.00 sec)
预期结果:
+----------+-------------+----------------+----------+
| addition | subtraction | multiplication | division |
+----------+-------------+----------------+----------+
| 8 | NULL | NULL | NULL |
| NULL | 4 | NULL | NULL |
| NULL | NULL | 12 | NULL |
| NULL | NULL | NULL | 3.0000 |
+----------+-------------+----------------+----------+
4 rows in set (0.00 sec)
+----------+-------------+----------------+----------+
| addition | subtraction | multiplication | division |
+----------+-------------+----------------+----------+
| 8 | 4 | 12 | 3.0000 |
+----------+-------------+----------------+----------+
1 row in set (0.00 sec)
你可以在下面试试-
SELECT
max(addition) as addition,max(subtraction) as subtraction, max(multiplication) as multiplication,max(division) as division
FROM
(
(SELECT
6 + 2 AS addition,
NULL AS subtraction,
NULL AS multiplication,
NULL AS division
FROM
DUAL)
UNION
(SELECT
NULL AS addition,
6 - 2 AS subtraction,
NULL AS multiplication,
NULL AS division
FROM
DUAL)
UNION
(SELECT
NULL AS addition,
NULL AS subtraction,
6 * 2 AS multiplication,
NULL AS division
FROM
DUAL)
UNION
(SELECT
NULL AS addition,
NULL AS subtraction,
NULL AS multiplication,
6 / 2 AS division
FROM
DUAL)
) A;
你可以在下面试试-
SELECT
max(addition) as addition,max(subtraction) as subtraction, max(multiplication) as multiplication,max(division) as division
FROM
(
(SELECT
6 + 2 AS addition,
NULL AS subtraction,
NULL AS multiplication,
NULL AS division
FROM
DUAL)
UNION
(SELECT
NULL AS addition,
6 - 2 AS subtraction,
NULL AS multiplication,
NULL AS division
FROM
DUAL)
UNION
(SELECT
NULL AS addition,
NULL AS subtraction,
6 * 2 AS multiplication,
NULL AS division
FROM
DUAL)
UNION
(SELECT
NULL AS addition,
NULL AS subtraction,
NULL AS multiplication,
6 / 2 AS division
FROM
DUAL)
) A;
这应该可以
SELECT
sum(isnull(addition,0)) addition
,sum(isnull(subtraction,0)) subtraction
,sum(isnull(multiplication,0)) multiplication
,sum(isnull(division,0)) division
FROM
(
(SELECT
6 + 2 AS addition,
NULL AS subtraction,
NULL AS multiplication,
NULL AS division
)
UNION
(SELECT
NULL AS addition,
6 - 2 AS subtraction,
NULL AS multiplication,
NULL AS division
)
UNION
(SELECT
NULL AS addition,
NULL AS subtraction,
6 * 2 AS multiplication,
NULL AS division
)
UNION
(SELECT
NULL AS addition,
NULL AS subtraction,
NULL AS multiplication,
6 / 2 AS division
)
) A
这应该可以
SELECT
sum(isnull(addition,0)) addition
,sum(isnull(subtraction,0)) subtraction
,sum(isnull(multiplication,0)) multiplication
,sum(isnull(division,0)) division
FROM
(
(SELECT
6 + 2 AS addition,
NULL AS subtraction,
NULL AS multiplication,
NULL AS division
)
UNION
(SELECT
NULL AS addition,
6 - 2 AS subtraction,
NULL AS multiplication,
NULL AS division
)
UNION
(SELECT
NULL AS addition,
NULL AS subtraction,
6 * 2 AS multiplication,
NULL AS division
)
UNION
(SELECT
NULL AS addition,
NULL AS subtraction,
NULL AS multiplication,
6 / 2 AS division
)
) A
Will,您将尝试运行上述查询。由于在调用本机函数“isnull”时导致参数计数不正确,因此您的查询结果与Will类似,因此您尝试运行上述查询。由于在调用本机函数“isnull”时导致参数计数不正确,所以您的查询结果如下