SQL DELETE DUPLICATE ROWS

If you have got a situation that you have multiple duplicate records in a table, so at the time of fetching records from the table you should be more careful. You make sure that you are fetching unique records instead of fetching duplicate records.

To overcome with this problem we use DISTINCT keyword.

It is used along with SELECT statement to eliminate all duplicate records and fetching only unique records.

SYNTAX:

The basic syntax to eliminate duplicate records from a table is:

SELECT DISTINCT column1, column2,....columnN  

FROM table _name  

WHERE [conditions]  

EXAMPLE:

Let us take an example of STUDENT table.

ROLL_NO	NAME	PERCENTAGE	ADDRESS
1	AJEET MAURYA	72.8	ALLAHABAD
2	CHANDAN SHARMA	63.5	MATHURA
3	DIVYA AGRAWAL	72.3	VARANASI
4	RAJAT KUMAR	72.3	DELHI
5	RAVI TYAGI	75.5	HAPUR
6	SONU JAISWAL	71.2	GHAZIABAD

Firstly we should check the SELECT query and see how it returns the duplicate percentage records.

SQL > SELECT PERCENTAGE FROM STUDENTS  

ORDER BY PERCENTAGE;  

PERCENTAGE
63.5
71.2
72.3
72.3
72.8
75.5

Now let us use SELECT query with DISTINCT keyword and see the result. This will eliminate the duplicate entry.

SQL > SELECT DISTINCT PERCENTAGE FROM STUDENTS  

ORDER BY PERCENTAGE;  

PERCENTAGE
63.5
71.2
72.3
72.8
75.5