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Difference between rank dense rank and row number in SQL Video Lecture | SQL Server Administration: Basic Tutorials - Database Management
FAQs on Difference between rank dense rank and row number in SQL Video Lecture - SQL Server Administration: Basic Tutorials - Database Management
| 1. What is the difference between rank, dense rank, and row number in SQL? |  |
Ans. Rank, dense rank, and row number are all functions used in SQL to assign a unique identifier to each row in a result set. The main difference between them is how they handle ties.
- Rank: Rank assigns a unique number to each row in the result set, but if there are ties (i.e., rows with the same values), it will assign the same rank to them and leave gaps in the ranking sequence. For example, if there are two rows with the highest value, they will both have a rank of 1, and the next row will have a rank of 3.
- Dense Rank: Dense rank also assigns a unique number to each row, but it does not leave gaps in the ranking sequence. If there are ties, it will assign the same rank to them and continue with the next sequential rank. For example, if there are two rows with the highest value, they will both have a dense rank of 1, and the next row will have a rank of 2.
- Row Number: Row number simply assigns a unique number to each row in the result set, regardless of ties. It does not consider the values in the rows or create any ranking sequence. Each row will have a different row number.
| 2. How do I use the rank function in SQL? | |
Ans. To use the rank function in SQL, you need to specify the column or expression you want to rank by in the ORDER BY clause. The rank function is then used in the SELECT statement to assign the rank to each row. Here's an example:
SELECT column1, column2, RANK() OVER (ORDER BY column1) AS Rank
FROM table_name;
This query will return the values from column1 and column2, along with the rank assigned to each row based on the values in column1. The result set will be sorted in ascending order of column1.
| 3. How can I use the dense rank function to handle ties in SQL? | |
Ans. To use the dense rank function to handle ties in SQL, you need to specify the column or expression you want to rank by in the ORDER BY clause. The dense rank function is then used in the SELECT statement to assign the dense rank to each row. Here's an example:
SELECT column1, column2, DENSE_RANK() OVER (ORDER BY column1) AS DenseRank
FROM table_name;
This query will return the values from column1 and column2, along with the dense rank assigned to each row based on the values in column1. The result set will be sorted in ascending order of column1, and ties will be assigned the same rank without leaving any gaps.
| 4. Can I use the rank function with multiple columns in SQL? | |
Ans. Yes, you can use the rank function with multiple columns in SQL. In the ORDER BY clause, you need to specify the columns in the desired order of ranking. Here's an example:
SELECT column1, column2, RANK() OVER (ORDER BY column1, column2) AS Rank
FROM table_name;
This query will return the values from column1 and column2, along with the rank assigned to each row based on the values in column1 and then column2. The result set will be sorted in ascending order of column1 and then column2.
| 5. How is the row number function different from the rank and dense rank functions in SQL? | |
Ans. The row number function is different from the rank and dense rank functions in SQL because it assigns a unique number to each row without considering the values in the rows or creating any ranking sequence. It simply assigns a sequential number to each row in the result set. Additionally, the row number function does not have an ORDER BY clause like the rank and dense rank functions. It can be used as follows:
SELECT column1, column2, ROW_NUMBER() OVER () AS RowNumber
FROM table_name;
This query will return the values from column1 and column2, along with the row number assigned to each row in the result set. The row numbers will be sequential and unique for each row.
Text Transcript from Video
this is part one 11 of signal server
tutorial in this video we'll discuss the
difference between rank dense rank and
row number functions in sequel server
first let's look at the similarities
between these three functions all these
three functions return an increasing
integer value starting at one based on
the ordering of rows imposed by the
order by clause if there are no ties if
there are ties then the rules are a bit
different which we will discuss in just
a bit for all these three functions
order by Clause is required partition by
clause is optional when the data is
partitioned the integer value is reset
to 1 when the partition changes so all
these are the similarities and another
important thing to keep in mind is that
all these three functions are going to
behave exactly the same way if we don't
have duplicate values in the column that
we are using in the order by Clause so
if you look at these three functions
here row number rank and dense rank we
know that for all these three functions
order by Clause is required so we are
using the order by Clause and then we
are sorting the data by salary column in
descending order and if you look at that
salary column in this table notice that
we don't have any duplicate values in
that column and if you look at what data
this query produces look at the row
number Rand and dense line functions all
three of them produce the same numbering
sequence that's how the behavior is
going to be if you don't have duplicate
values in the column that you have used
in the order by Clause of these three
functions now I have already typed this
exact same query here look at this when
we execute that we get the same
numbering sequence for all the three
functions that we have seen on the slide
if you want to see the difference
between these three functions then we
need to have some duplicate data in the
column that we have used in the order by
Clause so to get some duplicate data
what I'm going to do is delete the data
that we already have and this employee
is table and then I'm going to execute
this insert script right here and if you
look at this insert script notice that
for the first three rows we are in
certain same salary 8,000 now let's go
ahead and execute the same query and
look at the result we get we get a
different result now let's see that in
this PowerPoint slide you can actually
see it better here now look at this for
the first three rows we have the same
salary 8,000 so there is a tie between
those three rows in this case row number
function is still going to do it the
same way as it has been doing it's going
to assign an increasing unique number
for each row starting at one so it
starts from one goes all the way till
five even if there are ties whereas if
you look at the rank function for the
tide rules that is for the duplicate
rows it's giving the same rank one okay
and then if you look at the road that is
present after the tide rolls look at
that it didn't give it ramp to it has
skipped rank two three and four this
third row it has given I mean four
through it has given a rank of four okay
that means rank function is going to
skip rankings if there are duplicate
rows if you look at dense land function
this function just like rank function
it's going to assign the same rank where
we have ties so in this case it has
assigned one for the first three rows
and then for the fourth row that is
present
after the tide rolls it has given a rank
of two it didn't skip any rank so that's
the fundamental difference between these
three functions so here is the
difference row number returns an
increasing unique number for each row
starting at one even if there are
duplicates rank function returns an
increasing unique number for each row
starting at one when there are
duplicates same rank is assigned to all
the duplicate rows but the next row
after the duplicate rows will have the
rank it would have been assigned if
there had been no duplicates so rank
function skips rankings if there are
duplicates dense rank returns an
increasing unique number for each row
starting at one just like the rank
function when there are duplicates same
rank is assigned to all the duplicate
rows but the
Denzil and function will not keep any
ranks this means the next row after the
duplicate rows will have the next strand
in the sequence thank you for listening
and have a great day
tutorial in this video we'll discuss the
difference between rank dense rank and
row number functions in sequel server
first let's look at the similarities
between these three functions all these
three functions return an increasing
integer value starting at one based on
the ordering of rows imposed by the
order by clause if there are no ties if
there are ties then the rules are a bit
different which we will discuss in just
a bit for all these three functions
order by Clause is required partition by
clause is optional when the data is
partitioned the integer value is reset
to 1 when the partition changes so all
these are the similarities and another
important thing to keep in mind is that
all these three functions are going to
behave exactly the same way if we don't
have duplicate values in the column that
we are using in the order by Clause so
if you look at these three functions
here row number rank and dense rank we
know that for all these three functions
order by Clause is required so we are
using the order by Clause and then we
are sorting the data by salary column in
descending order and if you look at that
salary column in this table notice that
we don't have any duplicate values in
that column and if you look at what data
this query produces look at the row
number Rand and dense line functions all
three of them produce the same numbering
sequence that's how the behavior is
going to be if you don't have duplicate
values in the column that you have used
in the order by Clause of these three
functions now I have already typed this
exact same query here look at this when
we execute that we get the same
numbering sequence for all the three
functions that we have seen on the slide
if you want to see the difference
between these three functions then we
need to have some duplicate data in the
column that we have used in the order by
Clause so to get some duplicate data
what I'm going to do is delete the data
that we already have and this employee
is table and then I'm going to execute
this insert script right here and if you
look at this insert script notice that
for the first three rows we are in
certain same salary 8,000 now let's go
ahead and execute the same query and
look at the result we get we get a
different result now let's see that in
this PowerPoint slide you can actually
see it better here now look at this for
the first three rows we have the same
salary 8,000 so there is a tie between
those three rows in this case row number
function is still going to do it the
same way as it has been doing it's going
to assign an increasing unique number
for each row starting at one so it
starts from one goes all the way till
five even if there are ties whereas if
you look at the rank function for the
tide rules that is for the duplicate
rows it's giving the same rank one okay
and then if you look at the road that is
present after the tide rolls look at
that it didn't give it ramp to it has
skipped rank two three and four this
third row it has given I mean four
through it has given a rank of four okay
that means rank function is going to
skip rankings if there are duplicate
rows if you look at dense land function
this function just like rank function
it's going to assign the same rank where
we have ties so in this case it has
assigned one for the first three rows
and then for the fourth row that is
present
after the tide rolls it has given a rank
of two it didn't skip any rank so that's
the fundamental difference between these
three functions so here is the
difference row number returns an
increasing unique number for each row
starting at one even if there are
duplicates rank function returns an
increasing unique number for each row
starting at one when there are
duplicates same rank is assigned to all
the duplicate rows but the next row
after the duplicate rows will have the
rank it would have been assigned if
there had been no duplicates so rank
function skips rankings if there are
duplicates dense rank returns an
increasing unique number for each row
starting at one just like the rank
function when there are duplicates same
rank is assigned to all the duplicate
rows but the
Denzil and function will not keep any
ranks this means the next row after the
duplicate rows will have the next strand
in the sequence thank you for listening
and have a great day
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Nov 25, 2024 Last updated |
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