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...)

PREDICTION_DETAILS function in Oracle

When building predictive models the data scientist can spend a large amount of time examining the models produced and how they work and perform on their hold out sample data sets. They do this to understand is the model gives a good general representation of the data and can identify/predict many different scenarios. When the "best" model has been selected then this is typically deployed is some sort of reporting environment, where a list is (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...)

The best idea since 1992: Putting the C into ACID (We need your vote)

Oracle Rdb (only available for the VMS platform) supports SQL-92 assertions (http://community.hpe.com/hpeb/attachments/hpeb/itrc-149/22979/1/15667.doc) so why not Oracle Database? Let’s put the “C” into “ACID.”(read more)

Debug PL/SQL Web Pages

What happens when you can’t get a PL/SQL Web Toolkit to work because it only prints to a web page? That’s more tedious because any dbms_output.put_line command you embed only prints to a SQL*Plus session. The answer is quite simple, you create a test case and test it inside a SQL*Plus environment.

Here’s a sample web page that fails to run successfully …

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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 Developer & PL/SQL

While SQL Developer installs with a dbms_output view, some organizations close it before they distribute images or virtual machine (VM) instances. This post shows you how to re-enable the Dbms Output view for SQL Developer.

SQL Developer DBMS_OUTPUT Configuration

SQLDeveloper1

  1. You need to open SQL Developer, which may look like this when the DBMS_OUTPUT view isn’t visible.

SQLDeveloper1

  1. You need to click on the View menu option in SQL Developer and choose the Dbms Output dropdown menu (more...)

Subtleties – Part 1 (SQL and PL/SQL)

Almost every valid SQL statement (i.e., that is executed successfully by the SQL engine) can be embedded successfully as a static SQL in PL/SQL. Almost, but not every statement.
One example is the COLLECT aggregate function with the DISTINCT option.

To demonstrate it I’ll use the PROJECT_ASSIGNMENTS table, which contains assignments of people to projects. The same person may be assigned to the same project more than once, in different times.

create table  (more...)

Using a Sparse Index

My vacation from my blog is officially over. The question that I’m answering today is: How can you pass a set of non-sequential ID values to a function and return a result set?

You need to create three object types for this example. They are:

  • a list of numbers
  • a record structure, declared as an object type without methods
  • a list of the record structure

These are the SQL commands to create the required data (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...)

Who Rewrote My SQL?

There are several new features in Oracle 12c that are implemented under the hood by changing the SQL statement that we write to a different statement (e.g., by adding some hidden predicates).
In OUG Ireland 2016 I talked about two such features – In Database Archiving and Temporal Validity – as part of my “Write Less (Code) with More (Oracle12c New Features)” presentation. I usually talk about another such feature in this presentation (more...)

Mustererkennung mit MATCH_RECOGNIZE in 12c

Keith Laker hat im Data Warehouse Insider Blog eine Artikelserie begonnen, die sich mit der Verwendung des MATCH_RECOGNIZE Features in 12c beschäftigt. Ich will jetzt nicht behaupten, dass ich die Artikel umfassend wiedergeben würde (ja nicht einmal, dass ich sie komplett gelesen hätte), aber sie wären sicherlich ein sehr nützlicher Einstieg, sollte ich gelegentlich auf die Idee kommen, das Feature irgendwo einzusetzen. In erster Näherung greife ich hier aber nur die Zusammanfassungs-Abschnitte am jeweiligen Artikelende (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

The First and Last Word on NoSQL

Amazon had the first word on NoSQL but the creator of relational theory, Dr. E. F. Codd, gets the last word.(read more)

Auto DDL: delete obsolete columns from table

A quick one. In the past I used to generate ddl based on queries, like the following. But I find myself to re-invent them again. So to have it saved for my offspring: here's one on deleting obsolete columns as generated on importing an excel sheet in SQLDeveloper:


declare
l_schema_name varchar2(30) := 'MY_SCHEMA';
l_table_name varchar2(30) := 'A_TABLE';
cursor c_cols is
select column_name
from all_tab_columns col
where col.table_name = l_table_name
and col.owner = l_schema_name
(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...)