Difference between not null and Unique constraint in Oracle 10g.

Hello Guys,

Today we will see basic difference between not null and unique

constraints in Oracle 10g Database Software.

First, we will create table with 4 columns (eno , ename , edesi, esal ).

We will provide ename as not null and edesi as unique constraint.

Lets see...

We will try to enter null value in ename column.

Hence we can see that ename is not accepting null value and

displays error message as

cannot insert NULL into"SYSTEM.EMP.ENAME"

now lets try to enter repeat value(not unique) in edesi column.

Hence we can see that it shows error msg unique constraint

violated.

Here, ename can accept repeat value let's see.

Hence, we can see that ename can accept repeat value but edesi

can not as we have declared edesi as unique.

Thank you for watching.

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