Difference Betwixt Row_Number(), Rank() Together With Dense_Rank() Inwards Sql Server, Oracle.

Though all iii are ranking functions inwards SQL, likewise known every bit window business office inwards Microsoft SQL Server, the departure betwixt rank(), dense_rank(), in addition to row_number() comes when y'all convey ties on ranking i.e. duplicate records. For example, if y'all are ranking employees yesteryear their salaries so what would move the rank of 2 employees of same salaries? It depends on upon which ranking business office y'all are using e.g. row_number, rank, or dense_rank. The row_number() business office ever generates a unique ranking fifty-fifty amongst duplicate records i.e. if the ORDER BY clause cannot distinguish betwixt 2 rows, it volition nonetheless laissez passer on them different rankings, though which tape volition come upwards before or after is decided randomly e.g. inwards our illustration 2 employees Shane in addition to Rick convey the same salary in addition to has row disclose iv in addition to 5, this is random, if y'all run again, Shane mightiness come upwards 5th.

The rank() in addition to dense_rank() volition laissez passer on the same ranking to rows that cannot move distinguished yesteryear the lodge yesteryear clause, but dense_rank volition ever generate a contiguous sequence of ranks e.g. (1,2,3,...), whereas rank() volition move out gaps after 2 or to a greater extent than rows amongst the same rank (think "Olympic Games": if 2 athletes win the gilt medal, at that topographic point is no minute place, exclusively third).  You tin likewise run into T-SQL fundamentals or Querying Microsoft SQL Server to larn to a greater extent than near how rank in addition to dense_rank pause ties.

Surprisingly all these functions acquit similarly inwards Microsoft SQL Server in addition to Oracle, at to the lowest degree at the high level, so if y'all convey used them inwards MSSQL, y'all tin likewise job it on Oracle 11g or other versions.

SQL to develop schema
Here is the SQL to exercise tabular array in addition to insert roughly information into it for demonstration purpose:

IF OBJECT_ID( 'tempdb..#Employee' ) IS NOT NULL DROP TABLE #Employee;  CREATE TABLE #Employee (name varchar(10), salary int);  INSERT INTO #Employee VALUES ('Rick', 3000); INSERT INTO #Employee VALUES ('John', 4000); INSERT INTO #Employee VALUES ('Shane', 3000); INSERT INTO #Employee VALUES ('Peter', 5000); INSERT INTO #Employee VALUES ('Jackob', 7000); INSERT INTO #Employee VALUES ('Sid', 1000);

You tin run into that nosotros convey included 2 employees amongst same salaries i.e. Shane in addition to Rick, simply to demonstrate the departure betwixt row_number, rank, in addition to dense_rank window business office inwards SQL server, which is obvious when at that topographic point are ties inwards ranking.


ROW_NUMBER() Example
It ever generates a unique value for each row, fifty-fifty if they are same in addition to ORDER BY clause cannot distinguish betwixt them. That's why it is used to solve problems similar second highest salary or nth highest salary, nosotros convey seen earlier.

In the next example, nosotros convey 2 employees amongst the same salary in addition to fifty-fifty though nosotros convey generated row numbers over salary column it produces different row disclose for those 2 employees amongst the same salary.

select e.*, row_number() over (order by salary desc) row_number from #Employee e result: mention    salary  row_number Jackob  7000    1 Peter   5000    2 John    4000    3 Shane   3000    4 Rick    3000    5 Sid     1000    6

You tin run into inwards this illustration that nosotros convey ranked employees based upon their salaries in addition to each of them convey unique rank fifty-fifty if their salaries are same e.g. Shane in addition to Rick convey same salary 3000 but they got the unique rank quaternary in addition to 5th. It's worth knowing that inwards the instance of a tie, ranks are assigned on a random basis, see Querying Microsoft SQL Server to larn to a greater extent than near when to job the row_number() business office inwards SQL Server.

RANK() Example
The rank() business office volition assign the same rank to same values i.e. which are non distinguishable yesteryear ORDER BY. Also, the adjacent different rank volition non kickoff from forthwith adjacent disclose but at that topographic point volition move gap i.e. if quaternary in addition to fifth employee convey the same salary so they volition convey same rank 4, in addition to sixth employee which has different salary volition convey novel rank 6.

Here is the illustration to clarify the point:

select e.*, rank() over (order by salary desc) rank from #Employee e result: mention    salary  rank Jackob  7000    1 Peter   5000    2 John    4000    3 Shane   3000    4 Rick    3000    4 Sid     1000    6

You tin run into that both Shane in addition to Rick has got the same rank 4th, but the Sid got the rank 6th, instead of v because it buy the farm on master ordering.



DENSE_RANK() Example
The dense_rank business office is similar to rank() window business office i.e. same values volition move assigned the same rank, but the adjacent different value volition convey rank which is simply i to a greater extent than than the previous rank, i.e. if quaternary in addition to fifth employee has the same salary so they volition convey same rank but sixth employee, which has different salary volition convey rank 5, dissimilar rank vi every bit is the instance amongst rank() function. There volition move no gap on ranking inwards instance of dense_rank() every bit shown inwards the next example:

select e.*, dense_rank() over (order by salary desc) dense_rank from #Employee e mention    salary  dense_rank Jackob  7000    1 Peter   5000    2 John    4000    3 Shane   3000    4 Rick    3000    4 Sid     1000    5

You tin run into that both Shane in addition to Rick has same ranking 4th, but Sid at nowadays has fifth rank which is differnt than sixth inwards before illustration when nosotros used the rank() function. Btw, if y'all are serious to top dog SQL, I stronly sugest to read Joe Celko's SQL for Smarties, i of the to a greater extent than advanced mass inwards SQL.

Difference betwixt row_number vs rank vs dense_rank

As I told, the difference betwixt rank, row_number, in addition to dense_rank is visible when at that topographic point are duplicate records. Since inwards all our illustration nosotros are ranking records on salary, if 2 records volition convey the same salary so y'all volition notice the departure betwixt these iii ranking functions.

The row_number gives continuous numbers, piece rank in addition to dense_rank laissez passer on the same rank for duplicates, but the adjacent disclose inwards rank is every bit per continuous lodge so y'all volition run into a saltation but inwards dense_rank doesn't convey whatsoever gap inwards rankings.

-- departure betwixt row_number(), rank(), in addition to dense_rank() -- volition exclusively visible when at that topographic point were duplicates. -- row_number gives consecutive ranking fifty-fifty amongst duplicate -- rank in addition to dense_rank laissez passer on the same ranking but rank has a jump -- piece dense_rank doesn't convey jump  select e.*, row_number() over (order by salary desc) row_number,  rank() over (order by salary desc) rank, dense_rank() over (order by salary desc) as dense_rank  from #Employee e

in addition to hither is the output which clearly shows the departure inwards the ranking generated yesteryear rank() in addition to dense_rank() function:

You tin run into the employees Shane in addition to Rick convey same salary 3000 thence their ranking is same when y'all job the rank() in addition to dense_rank() but the adjacent ranking is vi which is every bit per continuous ranking using rank() in addition to v when y'all job dense_rank(). The row_number() doesn't pause ties in addition to ever laissez passer on a unique disclose to each record.

Btw, I ran all iii SQL queries on Oracle 11g R2 in addition to it gave me the same result. So, it seems both Oracle in addition to SQL Server back upwards these business office in addition to they acquit identically.


That's all near the difference betwixt ROW_NUMBER(), RANK() in addition to DENSE_RANK() business office inwards SQL SERVER. As I told, the departure boils downwards to the fact when ties happen. In the instance of the tie, ROW_NUMBER() volition laissez passer on unique row numbers, the rank volition laissez passer on the same rank, but the adjacent different rank volition non move inwards sequence, at that topographic point volition move a gap. In the instance of dense_rank, both rows inwards the necktie volition convey the same rank in addition to at that topographic point volition move no gap. The adjacent different rank volition move inwards sequence.

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