mysql

Question

我有这个table

我想要并且可以让它看起来像这样

我使用的查询是这样的 {

SELECT  Cat,Reg,Branch, Mnth, Qty
FROM
(
  SELECT Cat,Reg,Branch, 'Jan' Mnth, Jan Qty
  FROM BQV
  WHERE Jan > 0
  UNION ALL
  SELECT Cat,Reg,Branch, 'Feb', Feb
  FROM BQV

  UNION ALL
  SELECT Cat,Reg,Branch, 'Mar', Mar
  FROM BQV

UNION ALL
  SELECT Cat,Reg,Branch, 'Apr', Apr
  FROM BQV

UNION ALL
  SELECT Cat,Reg,Branch, 'May', May
  FROM BQV

UNION ALL
  SELECT Cat,Reg,Branch, 'Jun', Jun
  FROM BQV

UNION ALL
  SELECT Cat,Reg,Branch, 'Jul', Jul
  FROM BQV
  WHERE Feb > 0

  UNION ALL
  SELECT Cat,Reg,Branch, 'Aug', Aug
  FROM BQV

UNION ALL
  SELECT Cat,Reg,Branch, 'Sept', Sep
  FROM BQV

UNION ALL
  SELECT Cat,Reg,Branch, 'Oct', Octo
  FROM BQV

UNION ALL
  SELECT Cat,Reg,Branch, 'Nov', Nov
  FROM BQV

UNION ALL
  SELECT Cat,Reg,Branch, 'Dec', Dece
  FROM BQV

) QV

}

我可以通过视图或存储过程或其他方式实现吗？？我的 MySQL ver 是 5.5，它不能在视图中有子查询，我不能升级我的数据库，因为我不能承受任何损失或错误。

Answer 1

您不需要 Derived Table（它被 MySQL 错误地命名为 Subquery） , 只需删除它:

CREATE VIEW foo AS
SELECT Cat,Reg,Branch, 'Jan' AS Mnth, Jan AS Qty
FROM BQV
WHERE Jan > 0

UNION ALL
SELECT Cat,Reg,Branch, 'Feb', Feb
FROM BQV

UNION ALL
SELECT Cat,Reg,Branch, 'Mar', Mar
FROM BQV

UNION ALL
SELECT Cat,Reg,Branch, 'Apr', Apr
FROM BQV

UNION ALL
SELECT Cat,Reg,Branch, 'May', May
FROM BQV

UNION ALL
SELECT Cat,Reg,Branch, 'Jun', Jun
FROM BQV

UNION ALL
SELECT Cat,Reg,Branch, 'Jul', Jul
FROM BQV
WHERE Feb > 0

UNION ALL
SELECT Cat,Reg,Branch, 'Aug', Aug
FROM BQV

UNION ALL
SELECT Cat,Reg,Branch, 'Sept', Sep
FROM BQV

UNION ALL
SELECT Cat,Reg,Branch, 'Oct', Octo
FROM BQV

UNION ALL
SELECT Cat,Reg,Branch, 'Nov', Nov
FROM BQV

UNION ALL
SELECT Cat,Reg,Branch, 'Dec', Dece
FROM BQV

另一个解决方案是基于 CROSS JOIN 到第二个 table 存储月份名称 'Jan' 到 'Dec':

create table months ( mnth char(3));
insert into months values ('Jan'),('Feb'),...

select Cat,Reg,Branch, months.mnth, 
   case mnth 
     when 'Jan' then Jan
     when 'Feb' then Feb
     ...
     when 'Dec' then Dece
   end
from BQV CROSS JOIN months

Answer 2

下面的视图完美地满足了我的需要。

创建视图 scheme-test。trybqv1 作为

SELECT Cat,Reg,Branch, 'Jan' Mnth,Jan 数量来自 BQV A 联合所有 SELECT Cat、Reg、Branch，'Feb'，2 月来自 BQV

联合所有 SELECT Cat、Reg、Branch，'Mar'，三月来自 BQV

联合所有 SELECT Cat、Reg、Branch，'Apr'，四月来自 BQV

联合所有 SELECT Cat、Reg、Branch，'May'，五月来自 BQV

联合所有 SELECT Cat,Reg,Branch, 'Jun', 君来自 BQV

联合所有 SELECT Cat、Reg、Branch，'Jul'，7 月来自 BQV

联合所有 SELECT Cat、Reg、Branch，'Aug'，8 月来自 BQV

联合所有 SELECT Cat、Reg、Branch，'Sept'，9 月来自 BQV

联合所有 SELECT Cat、Reg、Branch、'Oct'、Octo 来自 BQV

联合所有 SELECT Cat、Reg、Branch，'Nov'，11 月来自 BQV

联合所有 SELECT Cat、Reg、Branch、'Dec'、Dece 来自 BQV

mysql - 子查询

mysql - subqueries

sql

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