The Twelve Days of NoSQL: Day Ten: Big Data

On the tenth day of Christmas, my true love gave to me Ten lords a-leaping. The topic of Big Data is often encountered when talking about NoSQL so let’s give it a nod. In 1998, Sergey Brin and Larry Page invented an algorithm for ranking web pages (The Anatomy of a Large-Scale Hypertextual Web Search […]

SQL utils using XML

You may have previously seen a short post I did on a SQL statement to identify which statements are using dynamic sampling.

If not, quick recap:

SELECT p.sql_id, t.val
FROM   v$sql_plan p
,      xmltable('for $i in /other_xml/info
                 where $i/@type eq "dynamic_sampling"
                 return $i'
                passing xmltype(p.other_xml)
                columns attr  (more...)

SQL Plan Management – 12C dumb feature

In Oracle 11G, Oracle introduced SQL Plan Management (SPM). It is excellent (I love it to bits). It allows you to create Baselines against SQL which lock-down the SQL execution plan. No more plan flips. More consistency. Perfect.

Whenever some Baselined SQL is ran, Oracle still parses it and compares (more...)

My history with Big Data

Before I joined Cloudera, I hadn't had much formal experience with Big Data. But I had crossed paths with one of its major use cases before, so I found it easy to pick up the mindset. My previous big project involved a relational database hooked up to a web server. (more...)

Largest Tables Including Indexes and LOBs

Just a quick code snippit. I do a lot of data pumps to move schemas between different databases; for example taking a copy of a schema to an internal database to try to reproduce a problem. Some of these schemas have some very large tables. The large tables aren’t always (more...)

Invisible Not Null Column

Yesterday I attended John King (@royaltwit) session on Oracle 12c for developers. He gave an overview of all the goodies that are available to us as developers. The whole plugging and unplugging of database, though very cool and exiting, is most likely not very relevant to most developers.
When he (more...)

Best Practice in 12c

Since PL/SQL now is closely integrated into SQL, we hence can happily state
sokrates@12.1 > with function bestpractice return varchar2
  2  is
  3  begin
  4     return 'Do not use PL/SQL when it can be done with SQL alone !';
  5  end bestpractice;
  6   (more...)

Recursive Subquery Factoring to the Rescue

Recursive subquery factoring (AKA Recursive Common Table Expressions) has been available in Oracle since version 11g R2 was launched sometime around 2009. I always thought of it as a replacement for the connect by clause and just another way to write hierarchical queries, so I never really took the time (more...)

Kitab incələmə: SQL asan yanaşma yolu (Genişləndirilmiş versiya)

(blog post in Azerbaijani)

Təqdimat mərasimi

Azərbaycan dilində informasiya texnologiyaları movzusunda yazılmış kitab çox azdır. Bu tip kitabların az olmasının ən böyük səbəbi İT sahəsinə aid rəsmi terminaloji tərcümənin olmamasıdır. Buna baxmayaraq son illərdə bir neçə texniki nəşrlə tanış olmaq imkanım olmuşdur. Bu kitablardan biri Samir Səmədov (OCM11g, www.ocm. (more...)


The PIVOT and UNPIVOT operators were introduced in Oracle 11g and the other day I helped out a friend using these operators.
He wanted the data in the columns to be "shifted to the left". To explain a little more, take a look at the following data:

ID V1 V2 (more...)

Fun with SQL – My Birthday

This year is kind of fun, my birthday is on November 12th (next Tuesday, if you want to send gifts). That means it will fall on 11/12/13. Even better perhaps, katezilla's birthday is December 13th. 12/13/14. What does this have to do with SQL?

Someone mentioned to me last night (more...)

Strange ORA-14196

It seems that sometimes you need a non-unique index to enforce a unique constraint even if this constraint is declared as not deferrable.

sokrates@11.2 > create table strange(i int not null, j int not null);

Table created.

sokrates@11.2 > alter table strange add constraint unique_i unique(i) not deferrable

New York Oracle User Group Fall Conference Materials

Thank you all who attended my sessions at NYOUG Fall Conference this morning. I appreciate spending you most precious commodity - your time - with me. I sincerely hope you found both the presentations enlightening as well as entertaining.

Please see the details of the sessions below along with the (more...)

DECOMPOSE this: when what you see is not exactly what you think you see

Always check out the original article at for latest comments, fixes and updates. I was trying to call function DECOMPOSE while investigating a strange problem I had with some Unicode strings that could not be properly indexed by Oracle Text and, amazingly, I found out that most (more...)


Those who visit often know what the title means. It’s a very simple yet powerful technique to group data which doesn’t seem appropriate for grouping at first sight.
I learned this very nice tip long time ago but often have to re-think before applying it to SQL or (more...)

An Attempt to Validate Email Addresses with a Regular Expression

After my Kscope13 presentation, one of the attendees approached me and asked if I had used regular expressions to try to validate email addresses. He didn’t know about regular expressions before the presentation and he was writing a PL/SQL function (which was getting very complex…) to accomplish this particular task. (more...)

DataDirect Access your favorite SaaS app with SQL

Database driver company   are writing the next generation of data access. They are working on a platform called Datadirect which will enable you to access loads of data sources in the cloud, from the cloud, and some of them with SQL

Yes you have (more...)

Let me SLEEP!

DBMS_LOCK is a slightly obscure built-in package. It provides components which so we build our own locking schemes. Its obscurity stems from the default access on the package, which is restricted to its owner SYS and the other power user accounts. Because implementing your own locking strategy is a good (more...)

Oracle 10g – a time traveller’s tale

Time travel sucks, especially going back in time. Nobody takes a bath, there are no anaesthetics and you can't get a decent wi-fi signal anywhere. As for killing your own grandfather, forget about it.

The same is true for going back in database versions. In 2009 I had gone straight (more...)

Where’s SCOTT?

The database on the Developer Days Database App VBox appliance doesn't have the SCOTT schema. This is fair enough, as the sample schemas aren't include by default any more (for security reasons, obviously). I know the official sample schemas used in the documentation - HR, OE, and so on - (more...)