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Pavol Z. Kutaj @pkutaj

CTEs Simplify Complex SQL Queries And Reduce Errors

CTEs (Common Table Expressions) are temporary result sets that can be referenced in SQL queries, improving code readability and modularity. They're not just a refactoring technique, but sometimes necessary for filtering derived columns.

usecase

The concern is documenting the use of COMMON TABLE EXPRESSIONS as used repeatedly in Redash when creating monitoring queries / reports. Also, I ran into the order of SQL operations learning that you cannot filter a derived column in the same statement where it is defined. 

  
  
  1. what is CTE

A CTE (Common Table Expression) is TEMPORARY RESULT SET 
You can reference within another SELECT, INSERT, UPDATE, or DELETE statement
i.e. you can build it and use in later query
used in more complex queries
they are EXPRESSIONS, i.e. they always return a value

  
  
  2. syntax...