A multi-join query evaluates the joins conceptually from left to right. So the result of one join is used as the left input to the next join. If you don’t understand this, you can end up with logical bugs, especially when outer joins are involved. (With inner and cross joins, the order cannot affect the meaning.)
- 4. Combining Sets
- from Training Kit (Exam 70-461): Querying Microsoft® SQL Server® 2012
- Publisher: Microsoft Press
- Released: December 2012
As an example, a multi-join that is set up first with a LEFT OUTER JOIN to preserve rows in a table and then an INNER JOIN to the right data elements from the previous LEFT OUTER JOIN to a new table could end up discarding some rows that were meant to be preserved.
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