The heart of row pattern matching is finding which row matches what part of the pattern. Within the 12c
DEFINElists the conditions a row may meet; it doesn't always work the way you expect, especially if you use aggregates in the condition.
I forgot to add a MATCH_RECOGNIZE solution to my last post on merging overlapping date ranges! That should take me just a few minutes, right? Wrong: it’s not that easy and here’s why. For test data, please refer to the previous post. To Merge or not to Merge? The idea is to merge date ranges if […]
A recent question on the OTN SQL forum asked how best to join two tables related by ID and date range, in order to insert one row per date into a data warehouse. One solution was to expand the data from each table, creating one row per date, then join on date. I think it's more efficient to join on date range, then expand.
It only works in version 12 :( That’s right, I didn’t test in previous versions and there was a bug. Please refer to the COMPARE_SYNC post for the new, improved version. Here is what I changed: The name is now COMPARE_SYNC. I don’t know what got into me to put those four meaningless letters in front. The […]
If a column or expression may be NULL, it is a pain to compare it to something else. Why? Because comparisons involving a NULL do not result in TRUE or FALSE: they result in NULL. I use the DECODE function to work around this problem: here's why - and how.
@thatjeffsmith recently recommended an article about making your blog more popular. The article said "lists of 10 things" were great ways to get more readers. Hey, if that's all it takes... STEW_COMPARE_SYNC is a package that generates SQL to compare data or synchronize tables. Here are 10 good reasons to use it.
Oracle Database 12c introduced "invisible columns": they are only visible when you name them explicitly in the
SELECTlist. Unfortunately, they seem to be even more invisible when you access them through a database link! Here are some surprising results from