1. What are the grouping function in SQL ?
2. If base table of a view deleted means, what will happen
while we querying on view ? will give any error ?
3. Difference between DROP, DELETE, TRUNCATE table ?
4. What is constraints and types ?
5. What is max size of nchar & nvarchar ?
6. Define ROLLBACK, COMMIT, SAVE POINT
7. How non-clustered better ? or rank the Clustered,
Non-Clustered and Table scan in performance wise
8. Select 10 rows from a table ?
9. Define DML, DDL, DCL, DTL commands ?
10. What is mean by NULL value ? NULL means "" or 0 or
undefined ?
11. Default constraints ?
12. Can we have more then primary Key in table ?
13. Type of integrity ? Entity, Referential, Domain ?
Answer Posted / mohammad ali
DML
DML is abbreviation of Data Manipulation Language. It is used to retrieve, store, modify, delete, insert and update data in database.
Examples: SELECT, UPDATE, INSERT statements
DDL
DDL is abbreviation of Data Definition Language. It is used to create and modify the structure of database objects in database.
Examples: CREATE, ALTER, DROP statements
DCL
DCL is abbreviation of Data Control Language. It is used to create roles, permissions, and referential integrity as well it is used to control access to database by securing it.
Examples: GRANT, REVOKE statements
TCL
TCL is abbreviation of Transactional Control Language. It is used to manage different transactions occurring within a database.
Examples: COMMIT, ROLLBACK statements
The DELETE command is used to remove rows from a table. A WHERE clause can be used to only remove some rows. If no WHERE condition is specified, all rows will be removed. After performing a DELETE operation you need to
COMMIT or ROLLBACK the transaction to make the change permanent or to undo it.
TRUNCATE removes all rows from a table. The operation cannot be rolled back. As such, TRUCATE is faster and doesn't use as much undo space as a DELETE.
The DROP command removes a table from the database. All the tables' rows,
indexes and privileges will also be removed. The operation cannot be rolled back.
DROP and TRUNCATE are DDL commands, whereas DELETE is a DML command. Therefore DELETE operations can be rolled back (undone), while DROP and TRUNCATE operations cannot be rolled back.
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