Going to UKOUG Tech14

I’m on my way to UKOUG Tech14, where I will present Database 12c MATCH_RECOGNIZE: Beating the Best Pre-12c Solutions on Tuesday at 3 P.M., room 4B. With all the Oaktable ACE Directors presenting at the same time, I don’t expect a big crowd but I’ll do my best for those who do turn up. This is my […]

Date Ranges in Data Warehouses using Oracle 12c

When you load data with an “effective date” into a Data Warehouse, what happens when the new data is the same as yesterday’s? Do you add a new record with the new “effective date” or do you update a date range in the existing record? At Open World last month, I got both answers: Tim Gorman […]

Statement-Level Atomicity

So important yet often ignored or misunderstood! No, not me, but “statement level atomicity”. Whenever you call the Oracle database to change data, the result will be all or nothing: Oracle will either do everything you asked it to, or nothing at all. This is true for SQL and PL/SQL. What the documentation says From […]

OpenWorld Presentation on Row Pattern Matching

You can download my presentation from http://www.slideshare.net/stewashton/row-patternmatching12coow14 Please download instead of viewing: the slideshare viewer doesn’t show the animations I worked so hard on. I have already blogged about some of the topics in my presentation. Sometime soon I will continue with in depth looks at other issues, such as “catastrophic backtracking”. To those many […]

Oracle 12c Row Pattern Matching: Beat the Best Pre-12c Solutions at OpenWorld!

Catchy title, don’t you think? My session has been moved to Monday 4 P.M., in direct conflict with Tom Kyte – and Keith Laker, who asked me to present in the first place. Avoid the lines: come see the MATCH_RECOGNIZE clause push great pre-12c solutions into retirement. As a bonus, be the first person on your block able […]

Rob van Wijk and ad hoc Grouping

In March 2014, I wrote about two methods for ad hoc grouping: “Grouping Sequences” and “Start of Group“. I just found out that Rob van Wijk wrote on the same subjects two months earlier. We even used the same example! I mention Rob’s article for two reasons: If my explanation wasn’t clear enough, you can try Rob’s. When […]

SQL and date ranges: don’t use NULL

We often use NULL values in date ranges, usually in the end date to signify the indefinite future. I have decided that this is a bad idea; here are my reasons. 1) NULL should not mean anything According to the SQL standard, NULL means “unknown”. That is why you can’t really compare a NULL value to anything, […]

SQL to find World Cup matches with comebacks

Lucas Jellema is writing a great series on SQL applied to the World Cup of football / soccer. In the article about finding matches with comebacks, he challenged readers to “find ‘dramatic comebacks’ where a team was two goals behind at some stage and yet managed to win the game.” Here is my reply, since replying […]

Bin Fitting problems with SQL

“Bin Fitting” or “Bin Packing” means putting the greatest quantity in the smallest number of “bins” or containers. There are some good solutions with the MODEL clause, but the most concise and efficient solutions use the new 12c MATCH_RECOGNIZE clause. There are two categories of “bin fitting” problems: The number of bins is fixed and the […]