Category: A Join A Day

• A Join A Day – Intersect

  

  2012-12-16 - A Join A Day, Fundamentals, General, Series, T-SQL Statements

  INTERSECT is a keyword that takes two query expressions and calculates the set theoretical intersection from the two row sets. Under the covers SQL Server often uses the Left Semi Join operator for INTERSECT queries. One peculiarity is, that duplicate rows will be removed from the final result.

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• A Join A Day – Right Anti Semi Join

  

  2012-12-15 - A Join A Day, Fundamentals, General, Series

  The Right Anti Semi Join, like the Right Semi Join, does not have a corresponding T-SQL statement. In the right circumstances however, the SQL Server optimizer will use the Right Anti Semi Join operator to build an efficient plan.

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• A Join A Day – The Left Anti Semi Join

  

  2012-12-14 - A Join A Day, Fundamentals, General, Series

  The Left Anti Semi Join is the polar opposite of the Left Semi Join. While it also only returns data from the left table, it returns only those rows that are not returned by the Left Semi Join. Read on to find out how to use it.

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• A Join A Day – The Right Semi Join

  

  2012-12-13 - A Join A Day, Fundamentals, General, Series

  The right semi join works like the left semi join, it just switches the role of the two sides. A Right Semi Join returns only rows from the right side base on the existence of matching rows on the left.

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• A Join A Day – The Left Semi Join

  

  2012-12-12 - A Join A Day, Fundamentals, General, Series

  The Left Semi Join is a half join: It only includes rows from the left side in the results. A typical example for a left semi join query is a statement containing the EXEISTS keyword. However, this does not always result in an execution plan with a Left Semi Join operator.

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