SQL Data Types

Date and Time Types in SQL :

Date : A calendar date containing a four-digit year, month and day of the month.

date ‘2001-04-25’

Time : The time of the day in hours, minutes and seconds.

time ’09:30:00’

Timestamp : the mixture of date and time.

timestamp ‘2001-04-25 10:29:01’

Note : SQL defines several functions to get the current_date and current_time.‘interval’ is another data type provided by SQL.

Default Values :

SQL allows a default value to be specified for an attribute.

Example-1 :        

Create table student
(ID varchar2(5),
Name varchar2(20) not null,
DNo  varchar2(10),
Tot_cred  number(3) default 0,
Primary key (ID) ) ;

Index Creation : 

An index on an attribute of a relation may be an arrangement that permits the database system to seek out those tuples within the relation that have a specified value for that attribute, effectively, without traversing every tuple of the relation.

Example-2: 

create index Faculty_Dept_index on faculty (dept) ;       

 This statement generates an index named ‘Faculty_Dept_index’ on the attribute dept of the relation faculty.