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AlwaysOn Architecture Guide: Building a High Availability and Disaster Recovery Solution by Using AlwaysOn Availability Groups

SQL Server 2012 AlwaysOn Availability Groups provides a unified high availability and disaster recovery (HADR) solution that improves upon legacy functionality previously found across disparate features. Prior to SQL Server 2012, several customers used database mirroring to provide local high availability within a data center, and log shipping for disaster recovery across a remote data center. With SQL Server 2012, this common design pattern can be replaced with an architecture that uses availability groups for both high availability and disaster recovery. This paper details the key topology requirements of this specific design pattern, including quorum configuration considerations, steps required to build the environment, and a workflow that shows how to handle a disaster recovery event in the new topology.

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The Seven Sins against T-SQL Performance

There are seven common antipatterns in T-SQL coding that make code perform badly, and three good habits which will generally ensure that your code runs fast. If you learn nothing else from this list of great advice from Grant, just keep in mind that you should 'write for the optimizer'.

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Adding new column with DEFAULT

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Comments posted to this topic are about the item Adding new column with DEFAULT

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Question of the Day

Adding new column with DEFAULT

Which number will the COUNT() return after executing the following statements: 

DROP TABLE IF EXISTS #test;
CREATE TABLE #test (id INT)
INSERT INTO #test (id)
SELECT *
  FROM GENERATE_SERIES(1, 3) AS gs
;

ALTER TABLE #test ADD flag BIT CONSTRAINT DF_#test_flag DEFAULT 0;
go
UPDATE #test SET flag = 0 WHERE id = 1
UPDATE #test SET flag = 1 WHERE id = 2

INSERT INTO #test (id) VALUES (4)

SELECT COUNT(*)
  FROM #test AS t
 WHERE flag = 0
 

See possible answers