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SQL and PL/SQL Articles

Timing an ALL_ROWS query

The Problem

A common complaint in SQL is that "it runs in 5 seconds in SQL*Plus, but takes hours in Production. Why?"

The reason is because SQL*Plus and most GUI SQL tools display rows as soon as they are fetched. In this way, you can SELECT * FROM big_big_table and it will display the first 20 or so rows in the table in a fraction of a second, then go back for more. The SQL is not really finishing in seconds; if you timed how long it took to retrieve every row, you'd see that it takes just as long as in Production.

PL/SQL Tuning for Batch Systems

A History Lesson

Where were you in 1990? Nelson Mandela was being freed from Victor Verster Prison after 26 years behind bars, Saddam Hussein was starting the Gulf War by invading Kuwait, and Tim Berners-Lee was inventing the World-Wide-Web at CERN in Geneva. Me? In 1990, I was writing an insurance system in Oracle SQL*Forms v2.3.

Selects, Cursors, RefCursors, Cursor Expressions, some simple examples of rowset manipulation in SQL and PL/SQL

Kevin Meade's picture

So a buddy of mine, Ray, asked me for some examples of how data could be returned from a PL/SQL procedure. After a short discussion and some fiddling in SQL*Plus, we produced a neat document with some easy examples of what he could do. I still don't know how he is hooking this up to his coding tools, but it is a good demonstration of alternatives for manipulating sets of rows so I figured I'd post it. Hope someone besides Ray finds it useful. Ray's original question was "Kev, is there a way to return data from PL/SQL code so I can use it like a set of rows?". If you are an advanced PL/SQL developer you probabely already know this stuff but then again, it might be worth a five minute look for you.

Easy XML - Let the Database do the Work

Kevin Meade's picture

I don’t want to learn XML. I don’t want to learn XPATH. I don’t want to learn XQUERY. I don’t want to learn XSLT. I don’t want to learn XSQL. I don’t want to learn XSU. XDB has some way cool stuff. But to-date, I have been pretty successful in not learning things I don’t want to learn. So you might think that when the time came for my databases to start sharing data via a XML transport, I would be in trouble. Fortunately, God gave me at least a few smarts when he loaded me up with laziness. In this article we will discuss one way to move XML formatted data in and out of Oracle using what we already know: object views, instead of triggers, collections, and PL/SQL packages.

What a strange way to write NULL

gojko's picture

A few days ago, while hunting for a bug in PL/SQL code, I stumbled upon the strangest way to write NULL. If the e-mail address parameter was empty, the genius who wrote this PL/SQL procedure set it to , then compared it with ten lines below, in order to log a problem. I really don't know what is it about NULL that scares people so much, but over the years I got used to occasional -1 and 0, or even 'EMPTY'. However, this is the first time I ran across Donald.

The Phoenix Rises: a How-To for SQL FROM SQL

Kevin Meade's picture

If I had to recommend THE one most exploitable skill to have for an Oracle Developer or DBA, it would have to be HOW TO PLAY GOLF. I have observed few other talents give regular Mary and Joe, greater access to people from all levels of the corporate world. You will meet everyone from the janitor, to management elite without the fear or intimidation that we sometimes feel in these circles. For some reason, on the fairway all are equal; the only things that matter are your swing and your handicap. Alas, I never learned to play golf, so I must settle for imparting an actual job skill. And for that, my best first choice would be SQL FROM SQL.

A better view

gojko's picture

Accessing the database from the outside world basically comes down to two options - direct querying or executing stored procedures. Procedural access is often chosen for the wrong reasons - making maintenance significantly harder.

10gR2 new feature: Case Insensitive Sorts & Compares

Natalka Roshak's picture

One handy new feature of 10gR2 is its vastly expanded ability to do case-insensitive sorts and compares (a subset of its expanded ability with other special sorts and compares, such as special linguistic sorts).

Best practice to corrupt data

gojko's picture

A common practice for handling errors in PL/SQL procedures is to catch all errors in the top-most database layer and convert them into error codes and human readable messages for client applications. This technique is a relict from the past and, in fact, a very bad practice from today's perspective, since it can lead to data corruption.

Display REFCURSOR results through SQL*Plus

Kevin Meade's picture

Recently a friend asked me a simple question; "How do I display the results of a REFCURSOR through SQL*Plus?". The answer is of course is just as simple as the question, you "SELECT" it like anything else. He just had not seen the syntax before. Being me though, I wouldn't let him get away with such an easy offing, so I sent him instead a quick write-up on REFCURSORS and, the just as interesting, CURSOR EXPRESSIONS. This write-up shows various coding samples of how to use these to great effect. He liked it. He said it should be written up somewhere, and I knew just where. Hope you like it too. If you do, please add something in a reply, especially if you have a better or unique or interesting way of exploiting these features. I'd like to read about it, maybe even steal your code...