Constraints

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Define based on business rulex.

1.       Not Null :

a.  Doesnot allow any  Null values.

b.   Can be define at column level only.

 





2.       Default :

a.       Filled with default value if we donot provide any value

b.      There is no restriction for the no of default value in one table.






3.       Check :

a.       Allows only a valid range of values

b.      Can be define at column level or table level.

c.       Can be define at one column only ( not more than one column)

d.      Cannot be define on composite key

4.       Unique :

a.       Doesnot allow duplicate value

b.      aLlow null values (any no. of null values)

c.       Null is not equal to null so multiple null values are allow

d.      Can be define on one or more that one columns

e.      Can be define at column and table level.

 

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