Guide for CTE in SQL Server

The Common Table Expression aka CTE in SQL Server provides a temporary result set in T-SQL. You can refer to it within a SQL Select, SQL Insert, SQL Delete, or SQL Update statement.

The option is available from SQL Server 2005 onwards, helping the developers write complex and long queries involving many JOINs, aggregation, and data filtering. Usually, developers use subqueries for writing T-SQL codes, and SQL Server stores these CTE in memory temporally until the query execution finishes. Once the query is finished, it is removed from memory.

CodingSight - Guide for CTE in SQL Server
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Everything You Need to Know About SQL CTE in One Spot

The first time Karl heard of SQL Server CTE was when he was looking for something to make his SQL code easier for the eye. It’s kind of a headache when you look at it. Anton, his concerned colleague, asked him about CTE. Karl thought Anton was referring to his headache. Maybe he heard it all wrong, so he answered, “Of course not.” The funny thing is, he was referring to Chronic Traumatic Encephalopathy, also a CTE – a neurodegenerative disease caused by repeated head injuries. But based on Karl’s response, Anton knew for sure that his colleague was clueless about what he was saying.

What a crazy way to introduce CTEs! So, before you get into the same boat, let’s clarify, what is SQL CTE or Common Table Expressions in the SQL world?

You can read the basics here. Meanwhile, we’ll learn a bit more about what happened in this unusual story.

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