Category Archives: General

Dynamic Pivot with SQL Macros in Oracle 20c

More than a year ago I blogged about my view on using Polymorphic Table Function (PTF) for dynamic pivot in Oracle 18c. Actually I was not as optimistic. The solution had at least two significant problems:

  • the function will not see any changes on the underlying data until new hard parse of the query
  • operating on bigger data sets returns multiple result rows: one per 1024 rows (the size of the row sets in PTF), thus requiring some post processing

With Oracle 20c we now have SQL macros and I was curious, whether they can help here.

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Building Hash Keys using SQL Macros in Oracle 20c

In the next post about SQL macros in Oracle 20c we look at how they could be useful for building hash keys. If you are familiar with Data Warehousing and Data Vault modelling approach, you will probably know why it can be a good idea to build hash keys or hash diffs. Anyway, we will not discuss whether or not you should use them, but rather how you can do this in Oracle in a consistent and performant way.

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Issue with the Hint ENABLE_PARALLEL_DML

Performing an ETL with large data sets, it is often a good idea to run DML in parallel. But, in contrast to parallel query or DDL, parallel DML have to be explicitly enabled. You had to issue ALTER SESSION ENABLE PARALLEL DML in the past. Starting with 12c you can enable parallel DML specifically for each query using the hint ENABLE_PARALLEL_DML. For a few years now, I’ve been using the hint now and then and was quite happy. An observation I made a few days ago can lead to a rethinking. What I could observe is that for the SQL with embedded hint a new child cursor was created each time. Let’s test it!

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Dynamic Pivot with Polymorphic Table Function?

LiveSQL is great place to start playing with new features. It provides a couple of very helpful demo scripts explaining how polymorphic table functions work. There I found a new script few days ago which uses PTF for dynamic pivot! WOW! According to my subjective perception, it seems to be one of the most desired features in Oracle SQL! But let’s have a closer look. Is this really feasible and mature enough to be used in production code?

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Polymorphic Table Functions (PTF) , Part 3 – Row Replication

In the third part of the PTF-series we learn how a PTF can change the cardinality of the input data flow: return more or less rows as in the input. We’ll use the same simple table as in the part 2 and our new task will be column transposing. We’ll still define, which columns have to stay unchanged (as we already did using the parameter cols2stay). All other columns should be displayed as key-value pairs. Continue reading

Polymorphic Table Functions (PTF) , Part 2 – More Basics With Some Deep-Dive

In the first part of PTF series we went through a very basic example removing some columns and adding a new column with a constant value. Starting from the same example we’ll do something more meaningful in the second part. How about concatenating the values of the removed columns as CSV in a new column? Continue reading

Polymorphic Table Functions (PTF) – Tinkering with Rowsets

Writing the second “basics” post on PTF I discovered, that there were much more details worth mentioning, than it would be acceptable for a “basics” post and would blow it up anyway 😉 So I decided to to separate the tests and finding in this (more deep-dive) post. Continue reading

Conditional Logic in SQL

A few days ago Sven Weller has published an excellent post about writing conditional logic in SQL and it reminded me of an example I used in one of my presentations. It is also about conditional logic in SQL but maybe some less obvious use cases in context of function calls and sorting. Continue reading

Polymorphic Table Functions Example – Transposing Columns To Rows

Hey, Oracle 18c is now available on the cloud and for engineered systems! For more than a week now. That also means you can play with it at LiveSQL. And of course you can try polymorphic table functions (PTF)! At least I’ve done that this weekend 😉 And here is my first working example. Continue reading