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SQL DISTINCT


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

 

 

Narayanaswamy

Hello! I am Narayanaswamy founder and admin of narayanatutorial.com. I have been working in IT industry more than 7 years. NarayanaTutorial is my web technologies blog. My specialties are Java / J2EE, Spring, Hibernate, Struts, Webservices, PHP, Oracle, MySQL, SQLServer, Web Hosting and Website Development.

I am a self learner and passionate about training and writing. I am always trying my best to share my knowledge through my blog.

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