How do you find data that is in one table but is not in another in SQL

Question

4.00/5 (1 vote)

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SQL-Server-2005

Good morning,

I am working with two SQL tables, one is a sort of "middle table" that is used to import data from individual offices to a "final table".

What I have been asked to do is to write a query that uses a specific identifying field to find out what are in the "middle table" but are not in the "final table".

The logic would be something like, "If *field* is in 'middle table' and 'final table'=True. If *field* is in 'middle table' but not in 'final table'= False. If True=disregard, if False=display results."

First, is my logic right?

Second, what SQL function would I use to make this happen?

Posted 18-Aug-11 2:41am

JT Jones

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3 solutions

Solution 3

SQL

SELECT foo
FROM middle_table a LEFT OUTER JOIN final_table b
ON a.foo = b.foo
WHERE b.foo IS NULL

Is an alternative method for getting the values from the middle table not in the final table

Posted 18-Aug-11 3:31am

Simon_Whale

Comments

Herman<T>.Instance 18-Aug-11 11:16am

In Oracle this was THE trick to do this. Fast and very functional in very large tables, so my 5

Simon_Whale 18-Aug-11 11:17am

Thanks :) Its also suprisingly quick in SQL Server too

Solution 2

I tend to use sql compare/[^] for this kind of task - admittedly it's not free, but it's a darn good bit of kit.

[Disclaimer]I don't and never have worked for Red Gate Software (I don't even knowingly know anyone who does)

Posted 18-Aug-11 3:06am

Reiss

Comments

[no name] 18-Aug-11 9:14am

A simple SQL statement will do the same thing, with no cost at all. Visual Studio also provides the same functionality.

Reiss 18-Aug-11 9:57am

true, just another way to do it that's all.

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Not Active · Accepted Answer · 2011-08-18T02:51:00

Solution 1

There is no SQL function for this, just code

SQL

SELECT foo
FROM middle_table
WHERE foo NOT IN(SELECT foo FROM final_table)

Posted 18-Aug-11 2:51am

Not Active

Comments

Reiss 18-Aug-11 9:10am

+5 - nice and simple