SQL DISTINCT

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In this tutorial post, we are going discussing how to Eliminating Duplicate Records from the table.

SQL DISTINCT

• The table could have duplicate row. In such case how to view only unique rows i.e distinct rows to achieve it DISTINCT clause can be used.
• The DISTINCT clause can be used to removing duplicate records from the result set. The DISTINCT clause can only be used with SELECT statements.
• The DISTINCT clause scans through the values of the columns specified and display only unique values from the result set.

 

Consider we have EMPLOYEE demo table which is using for the executing DISTINCT command

EMP_ID	EMP_NAME	EMP_DESIGNATION	EMP_GENDER	EMP_QUALIFICATION	EMP_LOCATION
100	Narayanaswamy	Sr.Software Engineer	Male	MCA	Chennai
101	Kumar	Quality Analyst	Male	B.Tech	Chennai
102	Ramesh	Database Administration	Male	B.Tech	Chennai
100	Narayanaswamy	Sr.Software Engineer	Male	MCA	Chennai

 

Selected all columns and all rows

 

Syntax:

SELECT DISTINCT  *  FROM <Table-Name>;

Query:

SELECT DISTINCT * FROM EMPLOYEE;

The above query scan entire rows, and eliminates rows which are having same content in each column.

Output

EMP_ID	EMP_NAME	EMP_DESIGNATION	EMP_GENDER	EMP_QUALIFICATION	EMP_LOCATION
100	Narayanaswamy	Sr.Software Engineer	Male	MCA	Chennai
101	Kumar	Quality Analyst	Male	B.Tech	Chennai
102	Ramesh	Database Administration	Male	B.Tech	Chennai

 

Selected columns and all rows

 

Syntax:

SELECT DISTINCT  <Column-Name 1>  FROM <Table-Name>;

Query:

SELECT DISTINCT EMP_QUALIFICATION FROM EMPLOYEE;

The above query scan entire rows, and eliminates rows which are having same content in EMP_QUALIFICATION column.

Output:

EMP_QUALIFICATION
MCA
B.Tech