ORACLE-BASE Blog Aggregator

Here’s a little quiz: If I take the average row length of the rows in a table, multiply by the number of rows, and convert the result to the equivalent number of blocks, how can the total volume of data in the table be greater than the total number of blocks below the table high […]

A recent posting on OTN came up with a potentially interesting problem – it started roughly like this: I have two queries like this: select * from emp where dept_id=10 and emp_id=15; select * from emp where dept_id=10 and emp_id=16; When I run them separately I get the execution plan I want, but when I run […]

Actually it’s probably not the NOT IN that’s nasty, it’s the thing you get if you don’t use NOT IN that’s more likely to be nasty. Just another odd little quirk of the optimizer, which I’ll demonstrate with a simple example (running under 11.2.0.3 in this case): This code is going to give you 10,000 rows […]

I wrote a note a few years ago about SQL*Net compression (this will open in a new window so that you can read the posts concurrently), showing how the order of the data returned by a query could affect the amount of network traffic. An example in the note demonstrated, using autotrace statistics that the number […]

I thought I’d try to spend some of today catching up on old comments – first the easier ones, then the outstanding questions on Oracle Core. The very first one I looked at was about pushing predicates, and the specific comment prompted me to jot down this little note about the 10053 trace file (the […]