Tag Archives: subquery

NOT IN vs. NOT EXISTS: The Negation Battle #JoelKallmanDay

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A year ago I wrote about the pitfalls of NULL values in NOT IN subqueries. This time I wanted to keep promises I made back then, dig a little deeper and also look at NOT EXISTS as another type of subquery used to filter out records based on negative matches. Is there any semantic difference and which is faster? Unfortunately, there are many myths and misconceptions around the usage of (NOT) IN and (NOT) EXISTS subqueries.

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Null Values? NOT IN my Subquery! #JoelKallmanDay

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I had to learn from this mistake more than once in my SQL career, until it became a kind of reflex: always think about the NULL values when you are writing a NOT IN subquery. Well, you should ALWAYS keep the NULL values in mind as a SQL developer, but in this case the consequences can be really nasty! And it drives me crazy how many times I’ve seen this error in my consulting life, even in production code. So, what is the point here?

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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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