Posts tagged with clause
It is a strange thing really: querying the database to find missing data. Queries usually report on what is there. Not the queries in this article (and its prequel): they report on what is not there. We explore a number of approaches to uncovering missing information – because the fact that something is not found in itself is a fact we may want to know about. And it gives me a nice motive to demonstrate a number of fun SQL features.
We are still very much engaged in the EMP and DEPT tables in the SCOTT schema that back in the early ’80s was pivotal in demonstrating the capabilities of the first Oracle RDBMS releases. It still does an excellent job for most of my demos today. Must be me…
This article delves into urgent matters such as ‘which letters do not occur in the names of the employees’, ‘in which months of the year was no one hired’, ‘who in each department does not have a colleague with less experience (or a lower salary)’, ‘which employees do not have a colleague in the same job (either in their own department or in the entire company)’, and more.
Retrieving the values for domains in SQL queries in the Oracle RDBMS – months, days, numbers and custom value sets1
It happens quite frequently that in our database applications – in queries or in PL/SQL packages – we need to use the values from more or less standard domains or custom lists of values. For example the list of all months in the year – to show a breakdown list of some measure per month. Or the days of the week, to do something similar. Sometimes we just need a list of numbers in a certain range. And it is quite common to outer join such a collection of domain values with the set of measurements, using the partition outer join feature – to ensure that for each category of measurements, there is an aggregate for each of the values in the domain.
This article demonstrates several examples of standard domains, some SQL tricks for composing domains out of thin air and a number of features to spell out numbers and internationalize days and month names.