Saturday, December 15, 2012

Left Outer Join , What is the Outer Join Table

I was little surprised when I heard the following statement which is,

When you are using Left Outer Join (even in Right Outer Join), Left joined table is defined by the ON condition not by the OUTER JOIN clause.

This means,

SELECT A.Column1, B.Column2

FROM A OUTER JOIN B ON A.ID = B.ID

Will give you every thing from the table A and from table B it gives you what only matches.

If you re-write the query, (You will notice that only change is, ON condition which is switched now)

SELECT A.Column1, B.Column2

FROM A OUTER JOIN B ON B.ID = A.ID

Will give you every thing from the table B and from table A it gives you what only matches.

What do you think?

Let us try it,

This is my sample data.

image

So let me try with two queries,

imageimage

Well, there is no truth what so ever.

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