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Explain various types of constraints in Oracle.Oracle "Check" Constraint:
It validates incoming columns at row insert time.
Not Null Constraint:
It is used to specify that a column may never contain a NULL value.
Primary Key Constraint:
It is used to identify the primary key for a table. This operation requires that the primary columns are unique, and it creates a unique index on the target primary key.
References Constraint:
This is the foreign key constraint and is only applied during INSERT and DELETE.
Unique Constraint:
It is used to ensure that all column values within a table never contain a duplicate entry.
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