More DBA job interview questions and answers at
http://dba.fyicenter.com/Interview-Questions/
(Continued from previous question...)
RDBMS FUNDAMENTALS - Organizing the Database
Base Tables : A database comprises base tables, which have the following features :
They physically exist on the disk, Each of them has a unique name and they contain data that is crucial to an organization.
Their attributes have data types such as character, integer, decimal, date and time.
CREATE TABLE : This is a DDL command in SQL that creates a new table in a database.
Syntax : CREATE TABLE table-name (column-name data-type [[size]]
NOT NULL/DEFAULT default-value]]
CHECK (column-name > 0)
UNIQUE (column-name)
PRIMARY KEY (column-name)
FOREIGN KEY (column-name) REFERENCES table-name)
ALTER TABLE : This is a DDL command in SQL that modifies the structure of an existing table.
Syntax : ALTER TABLE table-name
ADD (column-name data-type [[size]] [[NOT NULL DEFAULT]]...)
primary key definition / foreign key definition
DROP PRIMARY KEY / DROP FOREIGN KEY)
DROP TABLE : This is DDL command in SQL that deletes the an existing table. Once you delete a table, all data contained in it is lost and cannot be recovered. The storage space used by this table is also released.
Syntax : DROP TABLE table-name
(Continued on next question...)