SQL-使用XML路径查询

Question

I have the following query:

SELECT     ara.req_id
FROM        tbl_ara ara
WHERE       id in (
                        SELECT STUFF((
                        SELECT ',' + cast(id as varchar(8000))
                        FROM contact
                        WHERE ct_id = 2
                        FOR XML PATH('')
                        ), 1, 1, ''))

So, theres is table with name contact that I want to get all the ids when they are type of 2 . Then I am creating a list with Stuff. Then I want to use another table and get all the records that their id is on that list. You can see the logic in the query. The problem is that SQL doesn't recognise it as list and I get the following error:

Msg 245, Level 16, State 1, Line 11 Conversion failed when converting the nvarchar value '6019,49111,49112' to data type int.

Answer 1

STUFF in your case returns character data. From the documentation ( https://msdn.microsoft.com/en-us/library/ms188043.aspx ):

Returns character data if character_expression is one of the supported character data types. Returns binary data if character_expression is one of the supported binary data types.

So you do not get a list of IDs but rather a string containing numbers and commas.

Is there a reason for not using the IDs directly?

SELECT 
    [ara].[req_id]
FROM [tbl_ara] [ara]
WHERE [id] IN
             (
              SELECT 
                  [id]
              FROM [contact]
              WHERE [ct_id] = 2
             )

EDIT: Of course the JOIN solution by @gofr1 is a pretty good option, too.

Answer 2

The simplest way is JOIN:

SELECT ara.req_id
FROM tbl_ara ara
INNER JOIN contact c
    ON ara.id = c.id
WHERE c.ct_id = 2

If you want to run using STUFF then you should use dynamic SQL. At first prepare statement, then execute it:

DECLARE @sql nvarchar(max), @inpart nvarchar(max)

SELECT @inpart = STUFF((
                    SELECT ',' + cast(id as varchar(8000))
                    FROM contact
                    WHERE ct_id = 2
                    FOR XML PATH('')
                    ), 1, 1, '')


SELECT @sql = '
SELECT     ara.req_id
FROM        tbl_ara ara
WHERE       id in (' + @inpart+ ')'


PRINT @sql

--EXEC sp_executesql @sql

PRINT would get you this:

SELECT     ara.req_id
FROM        tbl_ara ara
WHERE       id in (6019,49111,49112)

Uncomment EXEC sp_executesql @sql to execute query.

Answer 3

Why don't you try this :

SELECT  ara.req_id
FROM    tbl_ara As ara
WHERE   Exists( Select  1
                From    contact As c
                Where   c.ct_id = 2
                        And c.id = ara.id
              )

As exists clause only check the existence of single match and return that row when match found.