Are you working with someone else’s schema and they haven’t declared nice names for all their constraints? Unfortunately, it is all too easy to create a table like this: Or like this: Sure, you get a little convenience when writing the table. But from now on, you’re stuck with weird, system generated names both for … Continue reading How to…
#constraints
5 posts
21 Oct 2016
14 Jul 2016
A lot of people use SQL constraints mainly to enforce data integrity, and that’s already a very good thing. A UNIQUE constraint, for instance, makes sure that there is at most one instance of any possible value (or tuple, in the case of a composite constraint) in a table. For instance: Constraints are also good … Continue reading How Adding…
11 Nov 2014
When writing DDL in SQL, you can specify a couple of constraints on columns, like NOT NULL or DEFAULT constraints. Some people might wonder, if the two constraints are actually redundant, i.e. is it still necessary to specify a NOT NULL constraint, if there is already a DEFAULT clause? The answer is: Yes! Yes, you … Continue reading Have You…
2 Sept 2014
CHECK constraints are already pretty great when you want to sanitize your data. But there are some limitations to CHECK constraints, including the fact that they are applied to the table itself, when sometimes, you want to specify constraints that only apply in certain situations. This can be done with the SQL standard WITH CHECK … Continue reading Awesome SQL…
26 May 2014
Yet Another 10 Common Mistakes Java Developers Make When Writing SQL (You Won’t BELIEVE the Last One)
jOOQ(Sorry for that click-bait heading. Couldn’t resist ;-) ) We’re on a mission. To teach you SQL. But mostly, we want to teach you how to appreciate SQL. You’ll love it! Getting SQL right or wrong shouldn’t be about that You’re-Doing-It-Wrong™ attitude that can be encountered often when evangelists promote their object of evangelism. Getting … Continue reading Yet Another…