Category Archives: 20c

Comparing Rows using a SQL Macro

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After the previous post about building an UNPIVOT query via SQL macro to output table rows like key-value pairs, I thought of another use case for the UNPIVOT operator, where developing a reusable SQL macro will make sense. From time to time you need to spot the difference between almost identical rows. You know they are different and you can easily check this using MINUS or GROUP BY, but if you want to know in what column(s) exactly the difference is, you need another approach.

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Using Subqueries and Views with PTF or SQL macros

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In the last post about SQL macros in 19c I tried to use a subquery as an input for the function. And when I had some DATE calculations in a query, I got ORA-62558: Unsupported data types (DATE) The result looked somewhat confusing at first, but if you think about it, it is logical and maybe not a bug at all. You should just be very explicit while using subqueries and views(!) in this scenario. And because this behavior is not documented, it is worth sharing, I think.

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Dynamic Pivot with SQL Macros in Oracle 20c

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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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Temporal Joins with SQL Macros in Oracle 20c

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In a previous post on SQL macros in Oracle Database 20c we saw how SQL macros can be used to create a kind of “parameterized” views to establish a simplified access tier to temporal data. In this post I’d like to explore more possibilities to hide the complexity of SQL statements behind a functional syntax provided by using SQL macros. As an example we’ll stay with a temporal data introduced in the previous post and explore how we can do a temporal join of this versioned data.

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Parameterized Views in Oracle? No problem! With SQL macros!

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Views have always been an efficient tool for encapsulating complex logic, creating defined access structures and so on. But there is one thing views cannot do: accept parameters. And this is unfortunately a big disadvantage in terms of flexibility. As a result, there are a number of workarounds, none of them without their drawbacks.

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Building Hash Keys using SQL Macros in Oracle 20c

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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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