Difference between revisions of "NOT NULL Column Constraint"
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==Purpose== | ==Purpose== | ||
Column constraint to disallow NULL values | Column constraint to disallow NULL values | ||
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==Syntax== | ==Syntax== | ||
NOT NULL | NOT NULL | ||
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==See Also== | ==See Also== | ||
| − | [[ALTER TABLE]], [[SQL Constraints|CONSTRAINTS]], [[CREATE TABLE]] | + | [[ALTER TABLE]], [[SQL Constraints|CONSTRAINTS]], [[CREATE TABLE]], [[Data_Attributes#Mandatory_input|Mandatory Input]] |
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==Description== | ==Description== | ||
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The NOT NULL column constraint is used to specify that the column cannot contain NULL values. The NULL column constraint can be used to allow NULL values. | The NOT NULL column constraint is used to specify that the column cannot contain NULL values. The NULL column constraint can be used to allow NULL values. | ||
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==Example== | ==Example== | ||
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[[Category:Documentation]] | [[Category:Documentation]] | ||
[[Category:SQL]] | [[Category:SQL]] | ||
Latest revision as of 12:41, 6 March 2015
Contents
Purpose
Column constraint to disallow NULL values
Syntax
NOT NULL
See Also
ALTER TABLE, CONSTRAINTS, CREATE TABLE, Mandatory Input
Description
A constraint is used to define rules that help to provide data integrity. Column constraints are specific to the column name specified. You must have ALTER privilege on the table. The table will be locked for EXCLUSIVE use during the operation.
The NOT NULL column constraint is used to specify that the column cannot contain NULL values. The NULL column constraint can be used to allow NULL values.
Example
ALTER TABLE customer; ADD COLUMN custref CHAR(5) NULL ALTER TABLE customer; ALTER COLUMN custref NOT NULL
