How to Delete a single row where there is no Primary key in the table and two rows have same values in a single column

In case we have a table that does have any primary key and contains two rows that have exactly same values. For e.g. consider a table named Dept which has two columns:

a. Deptno

b. Dname

And the data in the table is:

Deptno Dname

20 Marketing

We can see Deptno column contains two entries with value = 20 and Dname contains same values also. This happened as the record was inserted because, no primary key was present. We cannot delete the row with a delete command. In case we want to do the same we can use Common Table Expressions and Row_Number() function:

With MyCTE as

(

Select row_number() over (order by deptno) as 'RowNumber', * from Dept

)

Select * from MyCTE

The above command will get the following result:

RowNumber Deptno Dname

1 20 Marketing

2 20 Marketing

Now as we have generated RowNumber for a run time column, we can use the same to delete the row. So our command will be:

With MyCTE as

(

Select row_number() over (order by deptno) as 'RowNumber', * from Dept

)

Delete from MyCTE where RowNumber=1

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Rohit Dhand

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