Answer Posted / karthicksharma

As said earlier UNIQUE is a constraint and can be used
during a table creation to prevent duplication of data .

-----------------------------------------------------
CREATING A TABLE USING UNIQUE CONSTRAINT:
=================================================

eg:
SQL> create table empl1 (name varchar2(15),no number(5)
unique);

Table created.

-----------------------------------------------------

So from this it is clearly implied that UNIQUE constraint
is used to prevent INSERTION AS WELL AS RETRIVAL of non-
duplicate data.

whereas DISTINCT clause can only be used for RETRIVAL of
non-duplicate data.

Whereas DISTINCT is a clause and cannot be used during a
table creation to limit the duplication of data.

-----------------------------------------------------
CREATING A TABLE USING DISTINCT CLAUSE:
===========================================
eg:
create table empl2(name varchar2(15),no number(5) distinct)
*
ERROR at line 1:
ORA-00907: missing right parenthesis

-----------------------------------------------------

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