Interested to Buy Any Domain ? << Click Here >> for more details...
difference between table level constraint and column level and
advantages of table level constraint
- 4 Answers
- 15631 Views
- Doyensys, I also Faced
- E-Mail Answers
Answer Posted / santosh kumar
Let me explain both sides of the coin bit more clearly.
Table level Constraint
===========================
1. Constraints are defined separately after the columns are defined.
2. While defining constraints at this level constraint name must be provided
3. Not null constraints can't be defined at this level.
4. Composite keys can be defined at this level only.
A table level constraint can see every column in the table.
Column level Constraint
===========================
1. Constraints are defined along with the columns.
2. So constraint name is not required.
3. Not null constraints can be defined at this level only(NOT NULL constraint can only apply to one column).
4. Composite keys can't be defined at this level .
5. Column level constraint is more clear syntactically and more meaningful.
A column level constraint has scope only to the column it is defined on.
The major difference between the two constraint is the scope. So far as the use of constraints (validating proper data) is concerned they are pretty much the same.
Any column level constraint (exception: not null) can be expressed at the table level - but the opposite is not true.
Go for a column level constraint if the constraint is in fact a column constraint else use a table constraint.
It is recommended to always use a column constraint if the constraint applies just to the column (and NOT a table constraint if it only applies to a single column) - you can only do it at the column level.
| Is This Answer Correct ? | 6 Yes | 0 No |
Post New Answer View All Answers
Define join and name different types of joins?
Is left join faster than inner join?
Mention what does plv msg allows you to do?
What is a temporal table?
What is sql and also describe types of sql statements?
In what condition is it good to disable a trigger?
what are the advantages of mysql in comparison to oracle? : Sql dba
What are the types of functions in sql?
What is pl sql script?
what is the difference between delete and truncate statement in sql? : Sql dba
How to sort the rows in sql.
what is union? : Sql dba
What is #table in sql?
how to delete an existing column in a table? : Sql dba
Explain what is table in a database?
