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How to insert data from column A if column B is zero and from column B if column A is zero

I think I'm getting closer, but not sure:

I have an example table containing the email address of Personal and Work. I am trying to create a new table that contains one address.

Then insert the email address, for example: If the user has a work email, but does not have a personal email, an email to insert, and if there is no work email, insert a personal email.

The following code does not work, but it just shows some of the many options that I used:

USE EXAMPLE_DB

GO

CREATE TABLE USER_EMAIL(
 USER_NBR CHAR(1) NOT NULL
,EMAIL VARCHAR(30)NULL
)

GO

INSERT INTO USER_EMAIL(
 USER_NBR
,EMAIL
)

SELECT USER_NBR
,CASE WHEN EMAIL_ADDR IS NULL AND EMAIL_TYPE = 'Personal' THEN EMAIL_TYPE = 'Work' END EMAIL
,CASE WHEN EMAIL_ADDR IS NULL AND EMAIL_TYPE = 'Work'     THEN EMAIL_TYPE =  'Personal' END EMAIL
FROM EMAIL_DATA

Here is the table for EMAIL_DATA:

USER_NBR   EMAIL_TYPE       EMAIL_ADDR
1          Personal 
2          Personal     user2personal@demo.com
3          Personal         user3personal@demo.com
4          Personal 
5          Personal         user5personal@demo.com
1          Work         user1work@demo.com
2          Work         user2work@demo.com
3          Work 
4          Work         user4work@demo.com
5          Work

Thanks everyone!

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3 answers

row_number:

insert  user_email
        (user_nbr, email)
select  user_nbr
,       mail.email_addr
from    (
        select  user_nbr
        ,       email_addr
        ,       row_number() over (partition by user_nbr
                  order by
                  case 
                  when email_type = 'personal' then 1
                  when email_type = 'work' then 2
                  end) as rn
        from    email_data
        ) usr
where   usr.rn = 1

, left join :

insert  user_email
        (user_nbr, email)
select  user_nbr
,       coalesce(pers.email_addr, work.email_addr)
from    (
        select  distinct user_nbr
        from    email_data
        ) usr
left join 
        email_data as pers 
on      pers.user_nbr = usr.user_nbr
        and work.email_type = 'personal'
left join 
        email_data as work
on      work.user_nbr = usr.user_nbr
        and work.email_type = 'work'

, , cross apply:

insert  user_email
        (user_nbr, email)
select  user_nbr
,       mail.email_addr
from    (
        select  distinct user_nbr
        from    email_data
        ) usr
cross apply
        (
        select  top 1 *
        from    email_data mail
        where   mail.user_nbr = usr.user_nbr
                and mail.email_addr is not null
        order by
                case 
                when email_type = 'personal' then 1
                when email_type = 'work' then 2
                end
        ) mail
+2

, , , :

INSERT INTO USER_EMAIL(USER_NBR, EMAIL_ADDR)
SELECT USER_NBR, EMAIL_ADDR
FROM EMAIL_DATA
WHERE EMAIL_ADDR IS NOT NULL
+2

This does the following: If EMAIL_ADDRnull, it will look for the same table and look for an email of a different type of email for the same user. Did you want this?

INSERT INTO USER_EMAIL(
 USER_NBR
,EMAIL 
)
SELECT e.USER_NBR
     , EMAIL = COALESCE(e.EMAIL_ADDR
                    , (CASE e.EMAIL_TYPE
                        WHEN 'Work' THEN (SELECT TOP 1 EMAIL_ADDR  
                                      FROM EMAIL_DATA e1
                                      WHERE e1.USER_NBR=e.USER_NBR
                                      AND EMAIL_TYPE='Personal')
                        WHEN 'Personal' THEN (SELECT TOP 1 EMAIL_ADDR 
                                      FROM EMAIL_DATA e1
                                      WHERE e1.USER_NBR=e.USER_NBR
                                      AND EMAIL_TYPE='Work')
                    END))
FROM EMAIL_DATA e

Result with your data:

USER_NBR    EMAIL
1           user1work@demo.com
2           user2personal@demo.com
3           user3personal@demo.com
4           user4work@demo.com
5           user5personal@demo.com
1           user1work@demo.com
2           user2work@demo.com
3           user3personal@demo.com
4           user4work@demo.com
5           user5personal@demo.com
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