Suppose we have a table named EmployeeDeptInfo which have the column Employeid and Departmentid. The query for creating this table is given below:-
Employeeid contains the Id of the employee and Departmentid contains the Id of the department to which he/she is belonged. This table do not have any primary key defined on it and also it doesnt have any unique key constraint defined on any column.
Suppose the table contains the following data
In this table, entries for the employee having employeeid 2 & 3 are get repeated.In this example the data in the table is not much for the example point of view but in real time scenario it can be billions of rows and duplication of rows can be a very big concern. Therefore it is necessary to find out the duplicate rows in the table. We can use the Having Clause to find out the duplicate rows:-
Query for finding out the duplicate rows in the table:-
This query will give us the following results:-
We can also find out that how many times a record is repeated in the table. For example, The following query gives us the result of how many times a given record is repeated
This query will give us the following results
2 2 3
Here NoOfRepeat shows the number of times the records are duplicated in the table
This article shows that we can find the duplicate records with the help of the Group By and Having Clause.