Execution Plans

SQL Server execution-plans-3 book cover

Free eBook: SQL Server Execution Plans, Third Edition

  • Article

If a query is performing poorly, and you can't understand why, then that query's execution plan will tell you not only what data set is coming back, but also what SQL Server did, and in what order, to get that data. It will reveal how the data was retrieved, and from which tables and indexes, what types of joins were used, at what point filtering, sorting and aggregation occurred, and a whole lot more. These details will often highlight the likely source of any problem.

2020-12-23 (first published: )

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Technical Article

Changes to SQL Server 2012 Execution Plans

  • Article

I’ve been working with execution plans quite a lot in SQL Server 2012. There are a number of changes, most of them associated with new or different functionality. I had not noticed anything really fundamental until recently. I’ve become a huge proponent of always checking the properties of the SELECT statement. There’s so much useful information in there about what’s happened with the plan generation in the optimizer (not low level stuff, but the big picture items) that you should always be checking it first as a fundamental part of your plan examinations.

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2011-12-14

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Technical Article

Free ebook: SQL Server Execution Plans

  • Article

This free book is brought to you by Red Gate Software and Simple Talk Publishing. Why my query is running slow? Why isn't my index getting used? In order to answer these questions, you have to ask the same return question in each case: have you looked at the execution plan? Grant Fritchey provides the only dedicated and detailed guide to this essential topic.

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2011-07-11

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Question of the Day

Adding new column with DEFAULT II

Which number did the two COUNT(*) return:

DROP TABLE IF EXISTS #tmp
CREATE TABLE #tmp (id INT NOT NULL)

INSERT INTO #tmp (id) 
SELECT gs.value
  FROM GENERATE_SERIES(1, 5) AS gs

ALTER TABLE #tmp ADD my_value INT NOT NULL CONSTRAINT df_tmp_my_value DEFAULT 1

SELECT COUNT(*)  FROM #tmp AS t WHERE my_value = 1

ALTER TABLE #tmp DROP CONSTRAINT df_tmp_my_value

ALTER TABLE #tmp ADD CONSTRAINT df_tmp_my_value DEFAULT 2 FOR my_value

SELECT COUNT(*)  FROM #tmp AS t WHERE my_value = 1

See possible answers