Category Archives: SQL

Structured Query Language

MERGE Alias Bug – No Error Thrown When Using Wrong Alias


Back in the days, when I was just beginning working as an Oracle developer, I used to view Oracle Database Server as such a great piece of software to the extent where I wouldn’t even consider that a problem which I’ve just encountered wasn’t my fault, but Oracle’s bug!

Why am I bringing this up, you might ask? Well, a few weeks ago I’ve stumbled upon a weird bug in Oracle. I was using Oracle Take a look at the below example: Continue reading

Searching in the source of a view

Let's take a view at it

Once upon a time… I needed to check in the source of which objects a particular character string was included.

LONG (the pun!…) story short, non of the {USER|ALL|DBA}_SOURCE views give you a chance to search in the source of the views.

“Well, why is that a problem?!” – I hear you saying – “Don’t you know the {USER|ALL|DBA}_VIEWS views views (wait, one views too many)?”

O my, but of course! There’s a column named TEXT in them with the source of the views! Let’s try that: Continue reading

Answer to Quiz #2: NULL in Aggregate Functions

Mind the NULL!

1 Quiz #2 – NULL in Aggregate Functions

Hello again! It’s due time to provide the answers for my second quiz – the one about NULL in aggregate functions.

In this particular quiz, it wasn’t the point to pick the correct choices, but rather figure out what will be the result of running each of the SELECTs. Continue reading

Quiz #2: NULL in Aggregate Functions

Impact of NULL in Aggreaget Functions

Aww. So dusty in here. Where have I been for the past seven months?!

Either way, it’s that time. Yep, you know what I mean – it’s the QUIZ TIME!

I’ve got a new quiz for you today:

What will be the result of running each of the SELECTs? Continue reading

Text Index With a Sync Parameter

Subtitle is on holidays.

Oracle Text Index with SYNC (EVERY …) Parameter

Just a quick tip for today. Oracle allows us to create special kind of indexes on columns containing long texts. One of them is the CONTEXT type. You don’t need any particular privileges to create an index of this type (other than being able to create indexes in you schema). At least, that’s what the documentation says.

There was a question about creating a CONTEXT index on StackOverflow:

Can’t create oracle text index with sync every

Continue reading

Top-N Queries & The New Row Limiting Clause
11g & 12c

Sponsored by 'c'. Letter 'c'.

Getting the Top-N Records From an Ordered Set &
The New Row Limiting Clause – 11g & 12c

and a cup of tea if you’re lucky

I bet my cup of raspberry-juiced black tea that, somewhere along your journey with Oracle, you had to write a query which was supposed to return only the top-n rows from an ordered set. Unlike some of the other databases, MySQL, for instance, Oracle does not provide a dedicated solution to this problem.

At least, not before the 12c hit the stage.

Before I introduce you to the nice Row Limiting Clause, let me show you why the first solution that comes to mind to solve the problem at hand, in Oracle’s versions prior to 12c, is not the right one, and what voodoo tricks one has to perform to achieve the expected result. Continue reading