SQL-将字段数据分解为单独的行

例如，表alpha中给出了以下内容：

我如何将这些数据分解为：

Field1 | Field2 | Field3
------------------------
Foo    | Bar    | A
Foo    | Bar    | B
Foo    | Bar    | C
Foo    | Bar    | D

我肯定有一种奇特的加入技巧可以做到这一点，但我想不出来。速度优化不是优先事项-此查询仅用于一次性报告，所以我不介意它是否慢，因为糖蜜让我有机会煮咖啡

您可以尝试以下操作：

WITH CTE_LenF3 AS 
(
  -- find the length of each field3
  SELECT Field1, Field2, LEN(Field3) as Len_F3
  FROM alpha
)
,CTE_Numbers AS 
(
 --generate numbers from 1 to LEN(Filed3) for each field1,field2 combination
  SELECT Field1, Field2, 1 AS Nmb FROM CTE_LenF3
  UNION ALL
  SELECT c.Field1, c.Field2, Nmb + 1 FROM CTE_Numbers n
  INNER JOIN CTE_LenF3 c ON c.Field1 = n.Field1 AND c.Field2 = n.Field2
  WHERE Nmb + 1 <= LEN_F3
)
--join generated numbers with actual table and use substring to get the characters
SELECT a.Field1, a.Field2, SUBSTRING(a.Field3, n.Nmb, 1)
FROM CTE_Numbers n
INNER JOIN alpha a ON a.Field1 = n.Field1 AND a.Field2 = n.Field2
ORDER BY a.Field1, a.Field2, n.Nmb

您可以尝试以下操作：

WITH CTE_LenF3 AS 
(
  -- find the length of each field3
  SELECT Field1, Field2, LEN(Field3) as Len_F3
  FROM alpha
)
,CTE_Numbers AS 
(
 --generate numbers from 1 to LEN(Filed3) for each field1,field2 combination
  SELECT Field1, Field2, 1 AS Nmb FROM CTE_LenF3
  UNION ALL
  SELECT c.Field1, c.Field2, Nmb + 1 FROM CTE_Numbers n
  INNER JOIN CTE_LenF3 c ON c.Field1 = n.Field1 AND c.Field2 = n.Field2
  WHERE Nmb + 1 <= LEN_F3
)
--join generated numbers with actual table and use substring to get the characters
SELECT a.Field1, a.Field2, SUBSTRING(a.Field3, n.Nmb, 1)
FROM CTE_Numbers n
INNER JOIN alpha a ON a.Field1 = n.Field1 AND a.Field2 = n.Field2
ORDER BY a.Field1, a.Field2, n.Nmb

---

您可以通过以下步骤轻松完成此操作：

步骤1：创建一个sql表值函数，可以将单词拆分为字符。您可以通过运行以下脚本来完成

CREATE FUNCTION [dbo].[SPLITWORD](
@WORD VARCHAR(MAX) 
) RETURNS @words TABLE (item VARCHAR(8000))

 BEGIN
 declare @count int, @total int
 select @total = len(@WORD), @count = 0

 while @count <= @total
 begin
   insert into @words select substring(@WORD, @count, 1)
   select @count = @count + 1
 end

 RETURN
END

---

您可以通过以下步骤轻松完成此操作：

步骤1：创建一个sql表值函数，可以将单词拆分为字符。您可以通过运行以下脚本来完成

CREATE FUNCTION [dbo].[SPLITWORD](
@WORD VARCHAR(MAX) 
) RETURNS @words TABLE (item VARCHAR(8000))

 BEGIN
 declare @count int, @total int
 select @total = len(@WORD), @count = 0

 while @count <= @total
 begin
   insert into @words select substring(@WORD, @count, 1)
   select @count = @count + 1
 end

 RETURN
END

比如：

declare @alpha table (Field1 varchar(20), Field2 varchar(20), Field3 varchar(6))
insert into @alpha(Field1, Field2, Field3) values
('Foo','Bar','ABCD')

;With Numbers(n) as (
    select 1 union all select 2 union all select 3 union all
    select 4 union all select 5 union all select 6
)
select Field1,Field2,SUBSTRING(Field3,n,1)
from
    @alpha
        inner join
    Numbers
        on
            n <= LEN(Field3)

比如：

declare @alpha table (Field1 varchar(20), Field2 varchar(20), Field3 varchar(6))
insert into @alpha(Field1, Field2, Field3) values
('Foo','Bar','ABCD')

;With Numbers(n) as (
    select 1 union all select 2 union all select 3 union all
    select 4 union all select 5 union all select 6
)
select Field1,Field2,SUBSTRING(Field3,n,1)
from
    @alpha
        inner join
    Numbers
        on
            n <= LEN(Field3)

替换分隔符

---

用以下查询实现功能的任何方式替换分隔符

DECLARE @temp as table(newFiled3 varchar(1))
DECLARE @str_Value varchar(50),@count int,@i int=1
SET @str_Value=(SELECT Field3 FROM alpha)
SET @count=LEN(@str_Value)
WHILE(@i<=@count)
BEGIN
    INSERT INTO  @temp VALUES (SUBSTRING ( @str_Value ,@i , 1 ))
SET @i=@i+1
END


SELECT Field1,Field2,b.newFiled3 
FROM tblStudent a inner join @temp b ON a.Field1='Foo'

---

任何方式的循环都不是一个好方法，但我们仍然需要使用它，因为您的文件3 ABCD是动态的

以下查询以任何方式实现您的功能

DECLARE @temp as table(newFiled3 varchar(1))
DECLARE @str_Value varchar(50),@count int,@i int=1
SET @str_Value=(SELECT Field3 FROM alpha)
SET @count=LEN(@str_Value)
WHILE(@i<=@count)
BEGIN
    INSERT INTO  @temp VALUES (SUBSTRING ( @str_Value ,@i , 1 ))
SET @i=@i+1
END


SELECT Field1,Field2,b.newFiled3 
FROM tblStudent a inner join @temp b ON a.Field1='Foo'

---

无论如何，循环不是一个好方法，但我们仍然需要使用它，因为您的文件3 ABCD是动态的

字段3是否由任何东西（例如逗号）删除，或者仅仅是每个字符或…？字段3中的字符数是否固定？是否需要按每个字符拆分列3，或者是否有其他内容？可能的重复项没有delimeters，不固定，但最多6个字符，由每个字符分割字段3由任何字符（例如逗号）分割，或仅为每个字符或…？字段3中的字符数是否固定？是否需要按每个字符分割列3，或是否有其他内容？没有delimeters的可能重复，不固定，但最多6个字符，按每个字符分割