Misconceptions about (Regular) Views Revealed when Presenting Editioning Views

Sometimes when you present an advanced feature, questions from the audience reveal misconceptions about basic features.

It happens to me almost every time I talk about Edition-Based Redefinition. I present Editioning Views, and then I get questions that reveal misunderstandings about views in general.

One such misunderstanding is regarding what is kept in the view definition.

When we create a view as “select * from table”, the * is expanded to actual (more...)

Using dynamic tooltips in your Interactive Report


Inside an Interactive Report (IR) I had a comment column. The comments in this column could become really large and the users wanted the comments to be automatically trimmed if more then 60 characters were displayed. If the user moved the mouse above a trimmed comment then a tooltip should be display including all comment text.

My first idea was to check for existing plugins which could do this job for me. So I searched (more...)

Top N- queries: using the 12c syntax.

One of the new features with Oracle database 12c is the new syntax for Top N queries and pagination. Did we really need this? Should you choose for the new syntax over the way we used to do it, with an inline view? I think so, it simply adds syntactic clarity to the query, and in this blogpost I will show the difference between the "old" and the "new".

For the examples I will use (more...)

Accessing STATUS columns efficiently

A frequently reoccuring design problem with relational databases is the issue locating unprocessed rows in a large table, so we know which rows of data are still yet to be processed.

The problem with a STATUS column is that it generally has low cardinality; there are probably only a handful of distinct values [(C)omplete, (E)rror, (U)nprocessed or something like that]. Most records will be (C)omplete. This makes STATUS a poor candidate for standard B-Tree indexation. (more...)

Joining to a pipelined table function and “left correlation”

Oracle 11.2.0.4

A pipelined table function may be called from regular SQL using the TABLE collection expression, e.g.

SELECT *
FROM   TABLE(my_pipelined_function('ABC','DEF'));

where ‘ABC’ and ‘DEF’ are the inputs to the function.

What if you want to call the function repeatedly for several sets of inputs, e.g. testing the function for a variety of values? If those inputs are stored in a table somewhere, it ought to be as easy (more...)

Rounding amounts, divide cents over multiple lines

In previous articles I wrote about dealing with a missing cent when you need to divide a certain amount over multiple lines. In these articles, links are at the bottom, I described a method to calculate the difference on the last row.
Then a question arose (as a comment):
What if for example i have 42 records and i wish to divide 100 by 42. I would get a rounded value of 2.38. If (more...)

Subtleties – Part 2 (Nested Tables and Varrays)

In Part 1 we saw that the SQL function COLLECT with the DISTINCT option is not natively supported in PL/SQL.
One suggested workaround was to apply the SET function on the result of the “simple” COLLECT function (without the DISTINCT option).
This works fine, in both SQL and PL/SQL, as long as the collection type that we use is Nested Table.

create type integer_ntt as table of integer
/

select person_id,set(cast(collect(project_id) as integer_ntt)) project_id_list
 (more...)

SQL vs. Excel – Subgroup medians

Recently I ran across this post on how to do subgroup medians in Excel 2010. First you need to create a pivot table, then “do some copying and pasting and use a formula to make it happen”. In SQL you can do this with one command.

Suppose that you have the same table as the Excel article, something like this:

CREATE TABLE sampletab
(arrest_day_of_week varchar2(10), 
arrest_ts TIMESTAMP, 
fingerprint_ts TIMESTAMP (more...)

Side-effect of ALTER SESSION SET CURRENT_SCHEMA

For most of our database set-ups we use a different TEMP space for application users than for end-user/support/developer/reporting usage.
The intention is to minimise the potential impact of a rogue ad-hoc query on the main applicaiton.

However, turns out this is ineffective IF you use:

ALTER SESSION SET CURRENT_SCHEMA = main_app_schema;

This is documented but I wasn’t previously aware.
No surprise that this learning opportunity was presented as a direct result of a rogue query (more...)

Gear up for #AIOUG OTN Yathra’ 2016

Guys, AIOUG is back again with OTN Yathra’ 2016. It is a series of technology evangelist events organized by All India Oracle Users Group in six cities touring across the length and breadth of the country. It was my extreme pleasure to be the part of it in 2015 and I’m pleased to announce that … Continue reading

Got anyone who needs April Fooling?

Do you have a sql*plus user who really needs an April Fool’s joke played on them? With a little editing to their glogin.sql, every sql*plus session will exit with what appears to be a pseudo-random TNS error.

(Note: assumes a *nix environment that has sed, grep, awk installed and oerr properly working.)

[oracle@localhost ~]$ cd $ORACLE_HOME/sqlplus/admin
[oracle@localhost admin]$ mv  (more...)

Temporal validity, multiple end dates

Recently I got involved in a question on Temporal Validity Periods together with Chris Saxon, one of the askTom-answer team.

The question was along the lines of: "What if I have a single start date but two possible end dates. One of the end dates is filled automatically by a background proces (could be a job) while the other one is to signal that the end date is set manually by the user. Could you (more...)

WINDOW NOSORT STOPKEY + RANK()

Recently I found that WINDOW NOSORT STOPKEY with RANK()OVER() works very inefficiently: http://www.freelists.org/post/oracle-l/RANKWINDOW-NOSORT-STOPKEY-stopkey-doesnt-work
The root cause of this behaviour is that Oracle optimizes WINDOW NOSORT STOPKEY with RANK the same way as with DENSE_RANK:

rnk1
create table test(n not null) as 
  with gen as (select level n from dual connect by level<=100)
  select g2.n as n
  from gen g1, gen g2
  where g1.n<=10
/
create index ix_test on test(n)
/
exec  (more...)

Renaming #EM12c / #EM13c Targets

Oracle Enterprise Manager is a complex piece of software that many organizations are running now. Some organizations set out with a formalized naming standard; some do not. Those who do not ofter end up identifying a naming standard later down the road and then making requests to change the names of the targets being monitored. In order to do this, there are two ways:

1. Delete and rediscover the target and rename at time of (more...)

An old dog learns a new trick

Reports of this blogs death have been greatly exaggerated. It has been very quiet here though while I worked on getting the Swedish part of Miracle started. It is now rocking the Stockholm market so it’s time to get back into more geeky stuff.

Talking of which. I have encountered Liquibase for database versioning time after time and always come to the conclusion that it is not what a DBA want to use. I recently took (more...)

SQL: Texte mit Umlauten und Sonderzeichen normieren

Im heutigen Beispiel möchte ich einmal kurz aufzeigen, wie Sie einen Text nach Ihren Bedürfnissen hin normieren können. Ich habe dazu die bekanntesten Länder der Erde in einer WITH Clause zusammengefasst und bilde mir anhand des Namens einen später verwendbaren normierten String.

Der Zielstring muss GROSSGESCHRIEBEN sein und darf keine Umlaute (ÖÜÄöüäß) und Sonderzeichen (, '.()-) beinhalten.
Mehr »

if you write SQL, be specific!

Today  I got a ticket from a developer where he claimed Oracle has a bug somewhere. The reason for this claim was a statement similar to
SELECT *
FROM   table1
WHERE  tab1col1 IN
       (      SELECT 
tab1col1 
              FROM   table2)


This query returned rows.

But when he run the inner query on it's own, he received
ORA-00904: "TAB1COL1": invalid identifier
00904. 00000 -  "%s: invalid (more...)

Show all views including a specific string

Seems to be a simple problem and easy to fix. Actually it is not because if you try one of these examples then you will fail:
Mehr »

Oracle Spatial (Teil 3) – Entfernung von Punkten berechnen

Im heutigen Blogpost möchte ich kurz anhand eines Beispiels aufzeigen, wie Sie die Entfernung von SDO_GEOMTRY Punkten berechnen können. Hierbei gehe ich auch konkret auf das Problem des Verbindens von zwei Datenmengen anhand einer definierten Entfernung ein.
Mehr »

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