how can i find differnces between two tables - from two database - in t-sql ?

Hello ,

I've 2 databases : first and second.
first has a table person with an id
second has a table user with an id.

we have differences between the two databases.

my question
how can i have all the id that are in first and not in second ?
how can i have all the id that are in second and not in first ?

thank you in advance for you help.

toshi
Erwin PombettAsked:
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Jim HornMicrosoft SQL Server Developer, Architect, and AuthorCommented:
>how can i have all the id that are in first and not in second ?
Simple query with a LEFT JOIN (return all person p), and a WHERE to filter out those where no matching user.
SELECT p.*
FROM first.dbo.person p
   LEFT JOIN second.dbo.user u ON p.id = u.id
WHERE u.id IS NULL

Open in new window


>how can i have all the id that are in second and not in first ?
Just flip it around
SELECT p.*
FROM second.dbo.user u
   LEFT JOIN first.dbo.person p ON p.id = u.id
WHERE p.id IS NULL

Open in new window


There are a couple of other ways to do this, using IN and CROSS JOIN.

Btw the id's for people and user are likely the people id and user id, so you may have to look for foreign keys and use those. For example, table u has a person_id that correctly maps to the person table.
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Microsoft SQL Server 2008

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