T-SQL: How to Select Values in Value List that are

问题:

I have a list of e-mail addresses, some of them are in my table, some of them are not. I want to select all e-mails from that list and whether they are in the table or not.

I can get users whose mail adresses are in the table like this:
SELECT u.* FROM USERS u WHERE u.EMAIL IN ('email1', 'email2', 'email3')

But how can I select values in that list which are not exist in the table?

Moreover, how can I select like this:

E-Mail | Status
email1 | Exist  
email2 | Exist  
email3 | Not Exist  
email4 | Exist  

Thanks in advance.

回答1:

For SQL Server 2008

SELECT email,
       CASE
         WHEN EXISTS(SELECT *
                     FROM   Users U
                     WHERE  E.email = U.email) THEN 'Exist'
         ELSE 'Not Exist'
       END AS [Status]
FROM   (VALUES('email1'),
              ('email2'),
              ('email3'),
              ('email4')) E(email)  

For previous versions you can do something similar with a derived table UNION ALL-ing the constants.

/*The SELECT list is the same as previously*/
FROM (
SELECT 'email1' UNION ALL
SELECT 'email2' UNION ALL
SELECT 'email3' UNION ALL
SELECT 'email4'
)  E(email)

回答2:

You need to somehow create a table with these values and then use NOT IN. This can be done with a temporary table, a CTE (Common Table Expression) or a Table Values Constructor (available in SQL-Server 2008):

SELECT email
FROM
    ( VALUES 
        ('email1')
      , ('email2')
      , ('email3')
    ) AS Checking (email)
WHERE email NOT IN 
      ( SELECT email 
        FROM Users
      ) 

The second result can be found with a LEFT JOIN or an EXISTS subquery:

SELECT email
     , CASE WHEN EXISTS ( SELECT * 
                          FROM Users u
                          WHERE u.email = Checking.email
                        ) 
            THEN 'Exists'
            ELSE 'Not exists'
       END AS status 
FROM
    ( VALUES 
        ('email1')
      , ('email2')
      , ('email3')
    ) AS Checking (email)

回答3:

You should have a table with the list of emails to check. Then do this query:

SELECT E.Email, CASE WHEN U.Email IS NULL THEN 'Not Exists' ELSE 'Exists' END Status
FROM EmailsToCheck E
LEFT JOIN (SELECT DISTINCT Email FROM Users) U
ON E.Email = U.Email

回答4:

When you do not want to have the emails in the list that are in the database you'll can do the following:

select    u.name
        , u.EMAIL
        , a.emailadres
        , case when a.emailadres is null then 'Not exists'
               else 'Exists'
          end as 'Existence'
from      users u
          left join (          select 'email1' as emailadres
                     union all select 'email2'
                     union all select 'email3') a
            on  a.emailadres = u.EMAIL)

this way you'll get a result like

name | email  | emailadres | existence
-----|--------|------------|----------
NULL | NULL   | [e-mail]    | Not exists
Jan  | [e-mail] | [e-mail]     | Exists

Using the IN or EXISTS operators are more heavy then the left join in this case.

Good luck :)

回答5:

This Should work with all SQL versions.

SELECT  E.AccessCode ,
        CASE WHEN C.AccessCode IS NOT NULL THEN 'Exist'
             ELSE 'Not Exist'
        END AS [Status]
FROM    ( SELECT    '60552' AS AccessCode
          UNION ALL
          SELECT    '80630'
          UNION ALL
          SELECT    '1611'
          UNION ALL
          SELECT    '0000'
        ) AS E
        LEFT OUTER JOIN dbo.Credentials C ON E.AccessCode = c.AccessCode

回答6:

Use this : -- SQL Server 2008 or later

SELECT U.* 
FROM USERS AS U
Inner Join (
  SELECT   
    EMail, [Status]
  FROM
    (
      Values
        ('email1', 'Exist'),
        ('email2', 'Exist'),
        ('email3', 'Not Exist'),
        ('email4', 'Exist')
    )AS TempTableName (EMail, [Status])
  Where TempTableName.EMail IN ('email1','email2','email3')
) As TMP ON U.EMail = TMP.EMail