sql转换成视图时参数错误

Question

我是 sql 的新手，我想知道为什么当我在视图中创建 sql 查询时这个错误会出现

mysql 查询：

SELECT staffid AS staff,   
(SELECT count( feedback )FROM msqueue WHERE staffid = staff AND feedback =1) AS a,
(SELECT count( feedback )FROM msqueue WHERE staffid = staff AND feedback =2) AS b,
(SELECT count( feedback )FROM msqueue WHERE staffid = staff AND feedback =3) AS c,
(SELECT count( feedback )FROM msqueue WHERE staffid = staff AND feedback =4) AS d
FROM msqueue
GROUP BY staffid

这个查询结果就是我想要的

|staff| a | b | c | d |     
|d1111| 0 | 1 | 1 | 0 |    
|d1234| 1 | 2 | 4 | 0 |

但是当我将查询创建为视图时结果是

|staff| a | b | c | d |     
|d1111| 1 | 3 | 5 | 0 |    
|d1234| 1 | 3 | 5 | 0 |

请帮我看看这段代码是怎么回事..非常感谢

Answer 1

尝试

SELECT staffid AS staff,   
(SELECT count(*) FROM msqueue n WHERE n.staffid = m.staffid AND feedback =1) AS a,
(SELECT count(*) FROM msqueue n WHERE n.staffid = m.staffid AND feedback =2) AS b,
(SELECT count(*) FROM msqueue n WHERE n.staffid = m.staffid AND feedback =3) AS c,
(SELECT count(*) FROM msqueue n WHERE n.staffid = m.staffid AND feedback =4) AS d
FROM msqueue m
GROUP BY staffid

在您的原始查询中，您使用主 select 的列 staffid 的别名将其与子查询的 staffid 列配对。这不足以区分两列，因此您得到了每一行中所有内容的总和。通过在列名前面使用 table 别名 m 和 n 我们现在可以清楚地解决这两个问题列。

看这里：http://sqlfiddle.com/#!9/ab25a9/1

您甚至可以在子查询中省略 tables 别名，例如

SELECT staffid AS staff,   
(SELECT count(*) FROM msqueue WHERE staffid = m.staffid AND feedback =1) AS a,
(SELECT count(*) FROM msqueue WHERE staffid = m.staffid AND feedback =2) AS b,
(SELECT count(*) FROM msqueue WHERE staffid = m.staffid AND feedback =3) AS c,
(SELECT count(*) FROM msqueue WHERE staffid = m.staffid AND feedback =4) AS d
FROM msqueue m
GROUP BY staffid

http://sqlfiddle.com/#!9/ab25a9/2

编辑

在我这边 "clever-mouthing" 之后，我刚刚发现，您的原始陈述有效 - 至少 "on its own" (http://sqlfiddle.com/#!9/ab25a9/4)。我还没有尝试将其放在视图中。也许这就是事情开始出错的时候。更安全的选择肯定是使用 table 别名。

是的，当你把它放在一个视图中时，确实会出错！但是只要外部查询至少有一个 table 别名，一切就OK了：http://sqlfiddle.com/#!9/f5f1e/1

我首先使用 MySql 对其进行了测试，但是语句是相同的，并且在 SQL-服务器，看这里http://sqlfiddle.com/#!6/f5f1e/1

Answer 2

我无法访问 mysql 服务器来对此进行测试，但总的来说 SQL 这可能是一个更简单的解决方案：

SELECT 
   staffid AS staff,   
   SUM(CASE WHEN feedback = 1 THEN 1 ELSE 0 END) AS a,
   SUM(CASE WHEN feedback = 2 THEN 1 ELSE 0 END) AS b,
   SUM(CASE WHEN feedback = 3 THEN 1 ELSE 0 END) AS c,
   SUM(CASE WHEN feedback = 4 THEN 1 ELSE 0 END) AS d
FROM 
   msqueue
GROUP BY 
   staffid

sql转换成视图时参数错误

sql parameter error when convert into view

mysql

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sql-server

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