Row_Number generates a run-time column in the result set which generates sequential number to each row according to the column used in order by clause.
Syntax
Row_Number() over (order by col1, col2, ....n partition by col1, col2, ....n)
- Order By is mandatory. Row Number is assigned in the result set based on the column provided in Order By clause.
- Partition By is optional which groups the result set based on the column provided in Partition By clause wherein each group, the sequence starts with 1.
Let's create an Employee table on which we would see how it works.
- create table tblEmployee(
- EmpId char(7)
- , FirstName varchar(50)
- , LastName varchar(50)
- , Gender char(1)
- )
-
- insert into tblEmployee
- select 'EMP0001', 'Sandeep', 'Mittal', 'M' union all
- select 'EMP0003', 'Abhay', 'Kumar', 'M' union all
- select 'EMP0005', 'Priya', 'Gupta', 'F' union all
- select 'EMP0002', 'Reema', 'Gupta', 'F' union all
- select 'EMP0004', 'Ritesh', 'Kumar', 'M'
Now, we would generate a sequential number for all the employees using
Row_Number,
- select EmpId, FirstName, LastName, Gender
- , row_number() over (order by EmpId) as RowNum
- from tblEmployee
Output
Check out the result set where
RowNum is generated based on
EmpId provided in
Order By,
Multiple columns can be used in the
Order By clause,
Let's take another example where we would use multiple columns in
Order By clause,
- select EmpId, FirstName, LastName, Gender
- , row_number() over (order by FirstName, LastName) as RowNum
- from tblEmployee
Output
In the next example, we will see how
Partition By clause works,
- select EmpId, FirstName, LastName, Gender
- , row_number() over (partition by Gender order by EmpId) as RowNum
- from tblEmployee
Output
Check out the result set where
RowNum is generated starting from 1 for each group i.e.
Gender which is provided in
Partition By clause,
In
Partition By clause also, we can use multiple columns as in
Order By clause.