Is it possible to write a statement that selects a column from a table and converts the results to a string?
Ideally I would want to have comma separated values.
For example, say that the SELECT statement looks something like
SELECT column
FROM table
WHERE column<10
and the result is a column with values
|column|
--------
| 1 |
| 3 |
| 5 |
| 9 |
I want as a result the string "1, 3, 5, 9"
你可以这样做：
declare @results varchar(500)
select @results = coalesce(@results + ',', '') + convert(varchar(12),col)
from t
order by col
select @results as results
| RESULTS |
-----------
| 1,3,5,9 |
SQL Server 2017 中有一个新方法：
SELECT STRING_AGG (column, ',') AS column FROM Table;
这将为1,3,5,9您生产
select stuff(list,1,1,'')
from (
select ',' + cast(col1 as varchar(16)) as [text()]
from YourTable
for xml path('')
) as Sub(list)
SELECT CAST(<COLUMN Name> AS VARCHAR(3)) + ','
FROM <TABLE Name>
FOR XML PATH('')
当前接受的答案不适用于多个分组。
当您需要对列行值的类别进行操作时，请尝试此操作。
假设我有以下数据：
+---------+-----------+
| column1 | column2 |
+---------+-----------+
| cat | Felon |
| cat | Purz |
| dog | Fido |
| dog | Beethoven |
| dog | Buddy |
| bird | Tweety |
+---------+-----------+
我想要这个作为我的输出：
+------+----------------------+
| type | names |
+------+----------------------+
| cat | Felon,Purz |
| dog | Fido,Beethoven,Buddy |
| bird | Tweety |
+------+----------------------+
（如果你跟着：
create table #column_to_list (column1 varchar(30), column2 varchar(30))
insert into #column_to_list
values
('cat','Felon'),
('cat','Purz'),
('dog','Fido'),
('dog','Beethoven'),
('dog','Buddy'),
('bird','Tweety')
)
现在——我不想深入到所有的语法，但正如你所看到的，这对我们来说是最初的技巧：
select ',' + cast(column2 as varchar(255)) as [text()]
from #column_to_list sub
where column1 = 'dog'
for xml path('')
--Using "as [text()]" here is specific to the “for XML” line after our where clause and we can’t give a name to our selection, hence the weird column_name
输出：
+------------------------------------------+
| XML_F52E2B61-18A1-11d1-B105-00805F49916B |
+------------------------------------------+
| ,Fido,Beethoven,Buddy |
+------------------------------------------+
您可以看到它的局限性在于它仅用于一个分组（其中 column1 = 'dog'）并且它在前面留下了一个逗号，另外它的名字很奇怪。
因此，首先让我们使用“stuff”函数处理前导逗号并将我们的列命名为 stuff_list：
select stuff([list],1,1,'') as stuff_list
from (select ',' + cast(column2 as varchar(255)) as [text()]
from #column_to_list sub
where column1 = 'dog'
for xml path('')
) sub_query([list])
--"sub_query([list])" just names our column as '[list]' so we can refer to it in the stuff function.
输出：
+----------------------+
| stuff_list |
+----------------------+
| Fido,Beethoven,Buddy |
+----------------------+
最后，让我们把它混入一个 select 语句中，注意对 top_query 别名的引用定义了我们想要的 column1（在此处的第 5 行）：
select top_query.column1,
(select stuff([list],1,1,'') as stuff_list
from (select ',' + cast(column2 as varchar(255)) as [text()]
from #column_to_list sub
where sub.column1 = top_query.column1
for xml path('')
) sub_query([list])
) as pet_list
from #column_to_list top_query
group by column1
order by column1
输出：
+---------+----------------------+
| column1 | pet_list |
+---------+----------------------+
| bird | Tweety |
| cat | Felon,Purz |
| dog | Fido,Beethoven,Buddy |
+---------+----------------------+
我们完成了。
你可以在这里阅读更多：
这是创建可重用列以逗号分隔的字符串的尝试。在这种情况下，我只有一个具有值的字符串，我不想要空字符串或空值。
首先，我创建一个用户定义类型，它是一个单列表。
-- ================================
-- Create User-defined Table Type
-- ================================
USE [RSINET.MVC]
GO
-- Create the data type
CREATE TYPE [dbo].[SingleVarcharColumn] AS TABLE
(
data NVARCHAR(max)
)
GO
该类型的真正目的是简化创建标量函数以将列放入逗号分隔值中。
-- ================================================
-- Template generated from Template Explorer using:
-- Create Scalar Function (New Menu).SQL
--
-- Use the Specify Values for Template Parameters
-- command (Ctrl-Shift-M) to fill in the parameter
-- values below.
--
-- This block of comments will not be included in
-- the definition of the function.
-- ================================================
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author: Rob Peterson
-- Create date: 8-26-2015
-- Description: This will take a single varchar column and convert it to
-- comma separated values.
-- =============================================
CREATE FUNCTION fnGetCommaSeparatedString
(
-- Add the parameters for the function here
@column AS [dbo].[SingleVarcharColumn] READONLY
)
RETURNS VARCHAR(max)
AS
BEGIN
-- Declare the return variable here
DECLARE @result VARCHAR(MAX)
DECLARE @current VARCHAR(MAX)
DECLARE @counter INT
DECLARE @c CURSOR
SET @result = ''
SET @counter = 0
-- Add the T-SQL statements to compute the return value here
SET @c = CURSOR FAST_FORWARD
FOR SELECT COALESCE(data,'') FROM @column
OPEN @c
FETCH NEXT FROM @c
INTO @current
WHILE @@FETCH_STATUS = 0
BEGIN
IF @result <> '' AND @current <> '' SET @result = @result + ',' + @current
IF @result = '' AND @current <> '' SET @result = @current
FETCH NEXT FROM @c
INTO @current
END
CLOSE @c
DEALLOCATE @c
-- Return the result of the function
RETURN @result
END
GO
现在，要使用这个。我将要转换为逗号分隔字符串的列选择为 SingleVarcharColumn 类型。
DECLARE @s as SingleVarcharColumn
INSERT INTO @s VALUES ('rob')
INSERT INTO @s VALUES ('paul')
INSERT INTO @s VALUES ('james')
INSERT INTO @s VALUES (null)
INSERT INTO @s
SELECT iClientID FROM [dbo].tClient
SELECT [dbo].fnGetCommaSeparatedString(@s)
得到这样的结果。
抢，保罗，詹姆斯，1,9,10,11,12,13,14,15,16,18,19,23,26,27,28,29,30,31,32,34,35,36, 37,38,39,40,41,42,44,45,46,47,48,49,50,52,53,54,56,57,59,60,61,62,63,64,65, 66,67,68,69,70,71,72,74,75,76,77,78,81,82,83,84,87,88,90,91,92,93,94,98,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,120,121,122,123,124,125,126,127,128,129,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159
我将我的 SingleVarcharColumn 类型中的数据列设置为 NVARCHAR(MAX)，这可能会损害性能，但我正在寻找灵活性，并且它的运行速度足以满足我的目的。如果它是 varchar 并且宽度固定且较小，它可能会更快，但我还没有测试过。
ALTER PROCEDURE [dbo].[spConvertir_CampoACadena]( @nomb_tabla varchar(30),
@campo_tabla varchar(30),
@delimitador varchar(5),
@respuesta varchar(max) OUTPUT
)
AS
DECLARE @query varchar(1000),
@cadena varchar(500)
BEGIN
SET @query = 'SELECT @cadena = COALESCE(@cadena + '''+ @delimitador +''', '+ '''''' +') + '+ @campo_tabla + ' FROM '+@nomb_tabla
--select @query
EXEC(@query)
SET @respuesta = @cadena
END
您可以使用以下方法：
select
STUFF(
(
select ', ' + CONVERT(varchar(10), ID) FROM @temp
where ID<50
group by ID for xml path('')
), 1, 2, '') as IDs
Declare @temp Table(
ID int
)
insert into @temp
(ID)
values
(1)
insert into @temp
(ID)
values
(3)
insert into @temp
(ID)
values
(5)
insert into @temp
(ID)
values
(9)
select
STUFF(
(
select ', ' + CONVERT(varchar(10), ID) FROM @temp
where ID<50
group by ID for xml path('')
), 1, 2, '') as IDs
使用LISTAGG函数，例如。SELECT LISTAGG(colmn) FROM table_name;
+------+----------------------+
| type | names |
+------+----------------------+
| cat | Felon |
| cat | Purz |
| dog | Fido |
| dog | Beethoven |
| dog | Buddy |
| bird | Tweety |
+------+----------------------+
select group_concat(name) from Pets
group by type
在这里，您可以轻松地在单个 SQL 中获得答案，并且通过在 SQL 中使用 group by，您可以根据该列值分隔结果。您也可以使用自己的自定义分隔符来拆分值
结果：
+------+----------------------+
| type | names |
+------+----------------------+
| cat | Felon,Purz |
| dog | Fido,Beethoven,Buddy |
| bird | Tweety |
+------+----------------------+
使用最简单的方法 -
SELECT GROUP_CONCAT(Column) from table