Kaley's (mostly) Oracle Database Blog
Hi! I'm Kaley Crum, Oracle DBA.
Welcome to my (mostly) Oracle database blog.

Oracle

Nested Loops and Join Order

There’s actually a lot of subtleties to nested loops.  When they’re explained, they’re most commonly represented in the following fashion:

But!  That’s clearly overly simplified.

For example, if the Oracle code looked like that, then join order clearly wouldn’t matter for nested loops if both tables were being full scanned.  But, as you’ll see shortly, join order matters a lot!

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Splitting Rows Out with SQL

Suppose you have the following table:

It looks like this:

001_splitting_rows

But you want it to look like this:

How do you fix this using SQL? Continue Reading