Snowflake SQL: Making Schema-on-Read a Reality (Part 1) 

This is my 1st official post on the Snowflake blog in my new role as their Technical Evangelist. It discusses getting results from semi-structured JSON data using our extensions to ANSI SQL. Schema? I don’t need no stinking schema! Over the last several years, I have heard this phrase schema-on-read used to explain the benefit of […]

The Twelve Days of SQLT: Day Three: Just a Mess Without a Clue

P.O.I.S.E.D. is an acronym for a six-step performance tuning method; it stands for Problem, Observation, Interpretation, Solution, Execution, and Documentation. Every problem-solving exercise has these six stages, whether the exercise takes six minutes or six weeks.(read more)

Update multiple columns

The Twelve Days of SQLT: Day Two: Miles To Go Before We Sleep

SQLT adoption has been limited even though it is the best tool for investigating SQL performance: It is only available as a download from Oracle Support. It creates tables and PL/SQL procedures in the database. It does not support Statspack, only AWR. (read more)

The Twelve Days of SQLT: Day One: Do What You Do Do Well

In his fifteen years with Oracle Support, Carlos Sierra created and perfected a tool called SQLTXPLAIN (SQL Tuning and Explain Plan; SQLT for short) for SQL performance investigations. SQLT collects all the information that could possibly be required to investigate SQL performance including environment information, execution plan history, statistics history (system statistics, table statistics, index statistics), and object definitions.(read more)

A random string of digits


I needed to generate a random string with an exact length consisting of numeric digits, that I could send in an SMS to a user as a temporary account “pin”. DBMS_RANDOM.string is unsuitable for this purpose as its supported modes all include alphabetic characters. So I used DBMS_RANDOM.value instead. I call TRUNC afterwards to lop off the decimal portion.

select TRUNC(
from (select 6 digits from dual);


Filed (more...)

KScope 2016 Acceptances

I've never been to KScope. Yes never.

I've always wanted to. Each year you hear of all of these stories about how much people really enjoy KScope and how much they learn.

So back in October I decided to submit 5 presentations to KScope. 4 of these presentations are solo presentations and 1 joint presentation.

This week I have received the happy news that 2 of my solo presentations have been accepted, plus my joint (more...)

Using Apache Drill REST API to Build ASCII Dashboard With Node

Read this article on my new blog Apache Drill has a hidden gem: an easy to use REST interface. This API can be used to Query, Profile and Configure Drill engine. In this blog post I will explain how to use Drill REST API to create ascii dashboards using Blessed Contrib. The ASCII Dashboard looks like Prerequisites Node.js Apache Drill 1.2 For this post, you will use the SFO

Generierung von Bitlisten mit Hilfe von SQL am Beispiel einer Datum zu Monat Konvertierung

Ich hatte vor kurzem die Aufgabe erhalten eine Bitliste auf Basis eines Monats zu generieren.
Bedeutet, ich habe einen String mit 31 Zeichen der je Zeichen den Zustand 1 oder 0 einnehmen kann.
 - 1 steht für aktiv
 - 0 steht für inaktiv


Um dies anhand eines verständlichen Beispiels zu verifizieren, habe ich mir eine Dienstplan-Tabelle ausgedacht.
Mehr »

Ein griffiges Beispiel für Lateral Inline Views

Auf den Lateral Join, der in 12c eingeführt wurde, habe ich hier schon vor geraumer Zeit hingewiesen - aber was damals fehlte, war ein griffiges Beispiel dafür, was man damit eigentlich anstellen kann. Das hat nun Oren Nakdimon in Teil 7 seiner überaus lesenswerten Serie Write Less with More ergänzt. In seinem Beispiel wird eine Projekt-Tabelle mit einer last_days_to_show_in_reports Spalte vorgestellt, in der für die einzelnen Einträge unterschiedliche Zeiträume angegeben sind (als Anzahl von Tagen). (more...)

Did it really fix it 1: OFE & nasty FIRST_ROWS plan on

Plan degradations on upgrade are normal.

This one’s no different.

On further investigation, turned out application was setting optimizer_mode = first_rows somewhere.

First point about this is that first_rows really shouldn’t be used either as a hint or as an optimizer_mode.

What does FIRST_ROWS mean?
From 11g doco:

The optimizer uses a mix of costs and heuristics to find a best plan for fast delivery of the first few rows.

If any sort of (more...)

The Hitchhiker’s Guide to the EXPLAIN PLAN Part 41: Why has my SQL execution plan changed?—A checklist

If the inputs to the CBO change, the plan can change. For example, changes to bind variables can cause the plan to change when it is hard parsed. Therefore one should never be surprised when plans change.(read more)

SQL: Calculate the past time between two dates in percent

Just a simple example how easy APEX can handle this kind of problem.

We have today the 06.11.2015 (11-06-2015) and we have two date values 01.11.2015 and 30.11.2015.
Now I want to know how much time has past in percent since the beginning (01.11.2015):
Result: 17 %
Mehr »

SQL Tuning: Thinking in Sets / How and When to be Bushy

Below is a SQL statement from a performance problem I was looking at the other day.

This is a real-world bit of SQL which has slightly simplified and sanitised but, I hope, without losing the real-worldliness of it and the points driving this article.

You don’t really need to be familiar with the data or table structures (I wasn’t) as this is a commentary on SQL structure and why sometimes a rewrite is the best (more...)

Custom CSV Export as ZIP file

At the beginning of this year I wrote an article about "Custom CSV Export in APEX".

Now I want to extend the solution by an optional ZIP export.

You can not export several files at the same time with standard APEX features. For that you have to create a ZIP file including all the files you want to download.

I made an example application "Multi CSV Download as ZIP file" where you see a (more...)

Updating Identity Columns

During my presentation "Oracle 12c for Developers" at the Sloveninan and Croatian User Groups I got the same question twice about Indentity Columns:

Is it possible to update an Identity Column?
During the presentation I show how it is not possible to insert a value for a "Generated Always Identity" column.
Let's take a look at an example:

SQL> create table t
2 (id number generated as identity
3 ,name varchar2(35)
4 );

Table created.


SQL and PL/SQL icons and stickers

Over the past couple of weeks I've been preparing my slides and presentations for Oracle Open World (2015).

One thing that occurred to me was that there was no icon or image to represent Oracle SQL and PL/SQL. I needed something that I could include in my presentations to represent these.

After a bit of Tweeting it turns out that there is no (official) icons or images for Oracle SQL and Oracle PL/SQL.

So I (more...)

Fundamentals of SQL Writeback in Dodeca

One of the features of Dodeca is read-write functionality to SQL databases.  We often get questions as to how to write data back to a relational database, so I thought I would post a quick blog entry for our customers to reference.

This example will use a simple table structure in SQL Server though the concepts are the same when using Oracle, DB2, and most other relational databases.  The example will use a simple Dodeca (more...)


Often, the biggest problem with regular expressions is that those who use them sometimes don’t use them correctly. A great example occurs in the Oracle Database with the REGEXP_LIKE function. For example, some developer use the following to validate whether a string is a number but it only validates whether the first character is a number.

  lv_input  VARCHAR2(100 (more...)

Create MySQL Index

Indexes are separate data structures that provide alternate pathways to finding data. They can and do generally speed up the processing of queries and other DML commands, like the INSERT, UPDATE, REPLACE INTO, and DELETE statements. Indexes are also called fast access paths.

In the scope of the InnoDB Database Engine, the MySQL database maintains the integrity of indexes after you create them. The upside of indexes is that they can improve (more...)