Category Archives: DBMS

Canonical Cover

Whenever a user updates the database, the system must check whether any of the functional dependencies are getting violated in this process. If there is… Read More »


RAID, or “Redundant Arrays of Inexpensive Disks” is a technique which makes use of a combination of multiple disks instead of using a single disk… Read More »

Query Optimization

Query: A query is a request for information from a database. Query Plans: A query plan (or query execution plan) is an ordered set of… Read More »


ALL & ANY are logical operators in SQL. They return boolean value as a result. ALL ALL operator is used to select all tuples of… Read More »


SQL supports a special value known as NULL which is used to represent the values of attributes that may be unknown or not apply to… Read More »

SQL | WITH clause

The SQL WITH clause was introduced by Oracle in the Oracle 9i release 2 database. The SQL WITH clause allows you to give a sub-query… Read More »


The EXISTS condition in SQL is used to check whether the result of a correlated nested query is empty (contains no tuples) or not. The… Read More »