In this blog, we will discuss
about the SQL constraints like Primary Key, Not NULL etc. and what type of
constraints are available in SQL and their purposes.
SQL constrains is used to enforce
the data rule while inserting or updating record in table. If rule is not
satisfied, it will not allowed to complete the action. It ensures the data
accuracy and reliability in the table.
Following SQL constraints are
used in SQL:
- Primary
Key -
it uniquely identify each row in table but it cannot accept NULL
value
- Unique
Key -
it ensure the column’s value are not duplicate
- Foreign
Key – it enforce the integrity constraints and make sure the
referenced key is uniquely identify each row in the referenced table
- Check -
it ensure the inserted or updated value matched with given values
- Not NULL – it ensures the column cannot
accept NULL value
- Default – set default value for a column,
if value is not specified.
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