Tag: operators

An Introduction to the IS [NOT] DISTINCT FROM Predicate in SQL Server

Posted on by Ian

SQL Server 2022 introduced the IS [NOT] DISTINCT FROM predicate that compares the equality of two expressions and guarantees a true or false result, even if one or both operands are NULL.

Normally if we compare two NULL values, they will always be different (although this will depend on your ANSI_NULLS setting – setting ANSI_NULLS to OFF will result in NULLs being treated as equal). The IS [NOT] DISTINCT FROM predicate enables us to compare NULLs as though they’re equal, even when our ANSI_NULLS setting is set to ON.

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Why GENERATE_SERIES() Only Returns the First Value in the Series in SQL Server

Posted on by Ian

If you’re using the GENERATE_SERIES() function to create a series of numbers, but you’re finding that only the first value in the series is returned, it could be something very obvious.

The obvious reason this could happen is that your step value is too big. In particular, if the step is so big that it covers the whole series, then it stands to reason that there will only be one value in the series.

If this is an issue for you, you might want to check that you’re using an appropriate step value. Using a smaller step value can help to create a series with more values.

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Introduction to the GENERATE_SERIES() Function in SQL Server

Posted on by Ian

In SQL Server, the GENERATE_SERIES() function is a relational operator that returns a series of values between a given start and stop point. These are returned in a single-column table.

Although the GENERATE_SERIES() function only works with numeric values, we can combine it with other functions to create a series of dates.

The GENERATE_SERIES() function was introduced in SQL Server 2022 (16.x) and requires the compatibility level to be at least 160.

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How the SQL UNION Operator Deals with NULL Values

Posted on by Ian

The SQL UNION operator concatenates the results of two queries into a single result set. By default it returns distinct rows (i.e. it removes any redundant duplicate rows from the result set). But we can also use UNION ALL to return non-distinct rows (i.e. retain duplicates).

When it comes to NULL values, it’s pretty straight forward. SQL treats two NULL values as non distinct values. In other words, they’re duplicates.

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