Database Design

External Article

Facts and Fallacies about First Normal Form

  • Article

When discussing the normalisation process, it is always the First Normal Form that causes the most grief and confusion. Anith Sen takes up the challenge to explain, in simple terms, exactly what the First Normal Form really is, and why it is so important for Database Design. Along the way, he dispels some of the myths that have grown up around 1NF.

2009-06-09

5,827 reads

Technical Article

Perils of adding fields to database tables

  • Article

Adding a field to a database table is sometimes not as simple as it may seem. If certain situations are not considered when adding fields, you may find yourself looking at some long nights fixing database code. Today, database consultant Tim Chapman looks at two such scenarios, and how you can plan for their occurrence.

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2009-03-04

4,537 reads

External Article

Constraint Yourself!

  • Article

In his first article for Simple-Talk, Joe Celko demystifies the use of Constraints, and points out that they are an intrinsic part of SQL and are a great way of ensuring that a business rule is done one way, one place, one time.

2008-10-30

2,846 reads

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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