Aggregate and find most used room by customer using SQL
I am trying to find all bookings grouped by my customers, and only showing the most used room by them (and the count booked).
This is the query I have so far, but the problem is that it will show all their bookings and counts, I'm only interested in their most booked room, I'm not sure what the best function to use to achieve this. I thought querying by the account
table and then a subquery for getting the booking numbers but I feel this might be less efficient (especially as we have around 10M account records).
Schema:
CREATE TABLE rooms (
room_id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
room_name varchar(50)
);
CREATE TABLE bookings (
id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
account_id int,
room_id int
);
Sample data:
INSERT INTO rooms (room_id, room_name)
VALUES ('1', 'Suite A'),
('2', 'Suite B'),
('3', 'Suite C'),
('4', 'Suite D'),
('5', 'Suite X');
INSERT INTO bookings (account_id, room_id)
VALUES ('123', '1'),
('123', '1'),
('123', '1'),
('123', '1'),
('123', '1'),
('123', '2'),
('123', '3'),
('123', '4'),
('123', '4'),
('123', '5'),
('123', '1'),
('124', '4'),
('124', '5'),
('124', '1');
Query:
select account_id, count(room_id), room_id
from bookings
group by account_id, room_id
SQL Fiddle Link
Desired Output:
account_id | most booked room | count
123 | Room A | 2
124 | Room B | 30
sql tsql
add a comment |
I am trying to find all bookings grouped by my customers, and only showing the most used room by them (and the count booked).
This is the query I have so far, but the problem is that it will show all their bookings and counts, I'm only interested in their most booked room, I'm not sure what the best function to use to achieve this. I thought querying by the account
table and then a subquery for getting the booking numbers but I feel this might be less efficient (especially as we have around 10M account records).
Schema:
CREATE TABLE rooms (
room_id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
room_name varchar(50)
);
CREATE TABLE bookings (
id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
account_id int,
room_id int
);
Sample data:
INSERT INTO rooms (room_id, room_name)
VALUES ('1', 'Suite A'),
('2', 'Suite B'),
('3', 'Suite C'),
('4', 'Suite D'),
('5', 'Suite X');
INSERT INTO bookings (account_id, room_id)
VALUES ('123', '1'),
('123', '1'),
('123', '1'),
('123', '1'),
('123', '1'),
('123', '2'),
('123', '3'),
('123', '4'),
('123', '4'),
('123', '5'),
('123', '1'),
('124', '4'),
('124', '5'),
('124', '1');
Query:
select account_id, count(room_id), room_id
from bookings
group by account_id, room_id
SQL Fiddle Link
Desired Output:
account_id | most booked room | count
123 | Room A | 2
124 | Room B | 30
sql tsql
1
Sample data and desired results in the question would clarify what you want. I'm not sure why you set up a MySQL fiddle for a question tagged tsql.
– Gordon Linoff
Nov 13 '18 at 11:58
I have updated the question to include the desired output, tsql wasn't supported in the tool used but the question is for tsql not mysql hence the tags used.
– Imran
Nov 13 '18 at 12:07
add a comment |
I am trying to find all bookings grouped by my customers, and only showing the most used room by them (and the count booked).
This is the query I have so far, but the problem is that it will show all their bookings and counts, I'm only interested in their most booked room, I'm not sure what the best function to use to achieve this. I thought querying by the account
table and then a subquery for getting the booking numbers but I feel this might be less efficient (especially as we have around 10M account records).
Schema:
CREATE TABLE rooms (
room_id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
room_name varchar(50)
);
CREATE TABLE bookings (
id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
account_id int,
room_id int
);
Sample data:
INSERT INTO rooms (room_id, room_name)
VALUES ('1', 'Suite A'),
('2', 'Suite B'),
('3', 'Suite C'),
('4', 'Suite D'),
('5', 'Suite X');
INSERT INTO bookings (account_id, room_id)
VALUES ('123', '1'),
('123', '1'),
('123', '1'),
('123', '1'),
('123', '1'),
('123', '2'),
('123', '3'),
('123', '4'),
('123', '4'),
('123', '5'),
('123', '1'),
('124', '4'),
('124', '5'),
('124', '1');
Query:
select account_id, count(room_id), room_id
from bookings
group by account_id, room_id
SQL Fiddle Link
Desired Output:
account_id | most booked room | count
123 | Room A | 2
124 | Room B | 30
sql tsql
I am trying to find all bookings grouped by my customers, and only showing the most used room by them (and the count booked).
This is the query I have so far, but the problem is that it will show all their bookings and counts, I'm only interested in their most booked room, I'm not sure what the best function to use to achieve this. I thought querying by the account
table and then a subquery for getting the booking numbers but I feel this might be less efficient (especially as we have around 10M account records).
Schema:
CREATE TABLE rooms (
room_id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
room_name varchar(50)
);
CREATE TABLE bookings (
id int NOT NULL AUTO_INCREMENT PRIMARY KEY,
account_id int,
room_id int
);
Sample data:
INSERT INTO rooms (room_id, room_name)
VALUES ('1', 'Suite A'),
('2', 'Suite B'),
('3', 'Suite C'),
('4', 'Suite D'),
('5', 'Suite X');
INSERT INTO bookings (account_id, room_id)
VALUES ('123', '1'),
('123', '1'),
('123', '1'),
('123', '1'),
('123', '1'),
('123', '2'),
('123', '3'),
('123', '4'),
('123', '4'),
('123', '5'),
('123', '1'),
('124', '4'),
('124', '5'),
('124', '1');
Query:
select account_id, count(room_id), room_id
from bookings
group by account_id, room_id
SQL Fiddle Link
Desired Output:
account_id | most booked room | count
123 | Room A | 2
124 | Room B | 30
sql tsql
sql tsql
edited Nov 13 '18 at 12:10
Zohar Peled
52.7k73273
52.7k73273
asked Nov 13 '18 at 11:57
ImranImran
4,12574679
4,12574679
1
Sample data and desired results in the question would clarify what you want. I'm not sure why you set up a MySQL fiddle for a question tagged tsql.
– Gordon Linoff
Nov 13 '18 at 11:58
I have updated the question to include the desired output, tsql wasn't supported in the tool used but the question is for tsql not mysql hence the tags used.
– Imran
Nov 13 '18 at 12:07
add a comment |
1
Sample data and desired results in the question would clarify what you want. I'm not sure why you set up a MySQL fiddle for a question tagged tsql.
– Gordon Linoff
Nov 13 '18 at 11:58
I have updated the question to include the desired output, tsql wasn't supported in the tool used but the question is for tsql not mysql hence the tags used.
– Imran
Nov 13 '18 at 12:07
1
1
Sample data and desired results in the question would clarify what you want. I'm not sure why you set up a MySQL fiddle for a question tagged tsql.
– Gordon Linoff
Nov 13 '18 at 11:58
Sample data and desired results in the question would clarify what you want. I'm not sure why you set up a MySQL fiddle for a question tagged tsql.
– Gordon Linoff
Nov 13 '18 at 11:58
I have updated the question to include the desired output, tsql wasn't supported in the tool used but the question is for tsql not mysql hence the tags used.
– Imran
Nov 13 '18 at 12:07
I have updated the question to include the desired output, tsql wasn't supported in the tool used but the question is for tsql not mysql hence the tags used.
– Imran
Nov 13 '18 at 12:07
add a comment |
2 Answers
2
active
oldest
votes
You want the most common room per account. Statistically, this is called the mode.
You can calculate it using window functions:
select ar.*
from (select account_id, room_id, count(*) as cnt,
row_number() over (partition by account_id order by count(*) desc) as seqnum
from bookings
group by account_id, room_id
) ar
where seqnum = 1;
Here is the dbfiddle, using MySQL 8, so the syntax is more compatible with SQL Server.
In the event where there is an account with equal number of bookings in a venue... what is the output? and is it possible to say order by lastbookings.order_date
– Imran
Nov 13 '18 at 17:04
Can you also explain what thepartition
andover
functions are doing here, I'd like to understand how this works. Thanks!
– Imran
Nov 13 '18 at 17:08
@Imran . . . docs.microsoft.com/en-us/sql/t-sql/functions/…. If there are equal numbers, then an arbitrary matching value is returned. For the most recent room, you can useorder by count(*) desc, max(order_date) desc
.
– Gordon Linoff
Nov 13 '18 at 18:39
add a comment |
You can use correlated subquery
DEMO
select * from
(select account_id, count(room_id) as cnt, room_id
from bookings
group by account_id, room_id
)A inner join rooms on A.room_id=rooms.room_id
where cnt in (select max(cnt) from
(select account_id, count(room_id) as cnt, room_id
from bookings
group by account_id, room_id
)B where A.account_id=B.account_id)
In the demo provided this still shows more than one instance of eachaccount_id
– Imran
Nov 13 '18 at 12:14
it's because of your sample data - you can see that for 124 you've entered 1, 4, 5 room - so the room no is unique here, so for each room the count is one - in this case which one you want to pick
– fa06
Nov 13 '18 at 12:15
@fa06 whenever I tries to access the demo it redirects to the homepage of dbfiddle
– Sanal Sunny
Nov 13 '18 at 12:17
@SanalSunny - db-fiddle.com/f/hNedhkY8AHSYcVEVmrSV8q/0 - you need to exeute the query
– fa06
Nov 13 '18 at 12:18
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
You want the most common room per account. Statistically, this is called the mode.
You can calculate it using window functions:
select ar.*
from (select account_id, room_id, count(*) as cnt,
row_number() over (partition by account_id order by count(*) desc) as seqnum
from bookings
group by account_id, room_id
) ar
where seqnum = 1;
Here is the dbfiddle, using MySQL 8, so the syntax is more compatible with SQL Server.
In the event where there is an account with equal number of bookings in a venue... what is the output? and is it possible to say order by lastbookings.order_date
– Imran
Nov 13 '18 at 17:04
Can you also explain what thepartition
andover
functions are doing here, I'd like to understand how this works. Thanks!
– Imran
Nov 13 '18 at 17:08
@Imran . . . docs.microsoft.com/en-us/sql/t-sql/functions/…. If there are equal numbers, then an arbitrary matching value is returned. For the most recent room, you can useorder by count(*) desc, max(order_date) desc
.
– Gordon Linoff
Nov 13 '18 at 18:39
add a comment |
You want the most common room per account. Statistically, this is called the mode.
You can calculate it using window functions:
select ar.*
from (select account_id, room_id, count(*) as cnt,
row_number() over (partition by account_id order by count(*) desc) as seqnum
from bookings
group by account_id, room_id
) ar
where seqnum = 1;
Here is the dbfiddle, using MySQL 8, so the syntax is more compatible with SQL Server.
In the event where there is an account with equal number of bookings in a venue... what is the output? and is it possible to say order by lastbookings.order_date
– Imran
Nov 13 '18 at 17:04
Can you also explain what thepartition
andover
functions are doing here, I'd like to understand how this works. Thanks!
– Imran
Nov 13 '18 at 17:08
@Imran . . . docs.microsoft.com/en-us/sql/t-sql/functions/…. If there are equal numbers, then an arbitrary matching value is returned. For the most recent room, you can useorder by count(*) desc, max(order_date) desc
.
– Gordon Linoff
Nov 13 '18 at 18:39
add a comment |
You want the most common room per account. Statistically, this is called the mode.
You can calculate it using window functions:
select ar.*
from (select account_id, room_id, count(*) as cnt,
row_number() over (partition by account_id order by count(*) desc) as seqnum
from bookings
group by account_id, room_id
) ar
where seqnum = 1;
Here is the dbfiddle, using MySQL 8, so the syntax is more compatible with SQL Server.
You want the most common room per account. Statistically, this is called the mode.
You can calculate it using window functions:
select ar.*
from (select account_id, room_id, count(*) as cnt,
row_number() over (partition by account_id order by count(*) desc) as seqnum
from bookings
group by account_id, room_id
) ar
where seqnum = 1;
Here is the dbfiddle, using MySQL 8, so the syntax is more compatible with SQL Server.
edited Nov 13 '18 at 12:46
answered Nov 13 '18 at 12:00
Gordon LinoffGordon Linoff
762k35296400
762k35296400
In the event where there is an account with equal number of bookings in a venue... what is the output? and is it possible to say order by lastbookings.order_date
– Imran
Nov 13 '18 at 17:04
Can you also explain what thepartition
andover
functions are doing here, I'd like to understand how this works. Thanks!
– Imran
Nov 13 '18 at 17:08
@Imran . . . docs.microsoft.com/en-us/sql/t-sql/functions/…. If there are equal numbers, then an arbitrary matching value is returned. For the most recent room, you can useorder by count(*) desc, max(order_date) desc
.
– Gordon Linoff
Nov 13 '18 at 18:39
add a comment |
In the event where there is an account with equal number of bookings in a venue... what is the output? and is it possible to say order by lastbookings.order_date
– Imran
Nov 13 '18 at 17:04
Can you also explain what thepartition
andover
functions are doing here, I'd like to understand how this works. Thanks!
– Imran
Nov 13 '18 at 17:08
@Imran . . . docs.microsoft.com/en-us/sql/t-sql/functions/…. If there are equal numbers, then an arbitrary matching value is returned. For the most recent room, you can useorder by count(*) desc, max(order_date) desc
.
– Gordon Linoff
Nov 13 '18 at 18:39
In the event where there is an account with equal number of bookings in a venue... what is the output? and is it possible to say order by last
bookings.order_date
– Imran
Nov 13 '18 at 17:04
In the event where there is an account with equal number of bookings in a venue... what is the output? and is it possible to say order by last
bookings.order_date
– Imran
Nov 13 '18 at 17:04
Can you also explain what the
partition
and over
functions are doing here, I'd like to understand how this works. Thanks!– Imran
Nov 13 '18 at 17:08
Can you also explain what the
partition
and over
functions are doing here, I'd like to understand how this works. Thanks!– Imran
Nov 13 '18 at 17:08
@Imran . . . docs.microsoft.com/en-us/sql/t-sql/functions/…. If there are equal numbers, then an arbitrary matching value is returned. For the most recent room, you can use
order by count(*) desc, max(order_date) desc
.– Gordon Linoff
Nov 13 '18 at 18:39
@Imran . . . docs.microsoft.com/en-us/sql/t-sql/functions/…. If there are equal numbers, then an arbitrary matching value is returned. For the most recent room, you can use
order by count(*) desc, max(order_date) desc
.– Gordon Linoff
Nov 13 '18 at 18:39
add a comment |
You can use correlated subquery
DEMO
select * from
(select account_id, count(room_id) as cnt, room_id
from bookings
group by account_id, room_id
)A inner join rooms on A.room_id=rooms.room_id
where cnt in (select max(cnt) from
(select account_id, count(room_id) as cnt, room_id
from bookings
group by account_id, room_id
)B where A.account_id=B.account_id)
In the demo provided this still shows more than one instance of eachaccount_id
– Imran
Nov 13 '18 at 12:14
it's because of your sample data - you can see that for 124 you've entered 1, 4, 5 room - so the room no is unique here, so for each room the count is one - in this case which one you want to pick
– fa06
Nov 13 '18 at 12:15
@fa06 whenever I tries to access the demo it redirects to the homepage of dbfiddle
– Sanal Sunny
Nov 13 '18 at 12:17
@SanalSunny - db-fiddle.com/f/hNedhkY8AHSYcVEVmrSV8q/0 - you need to exeute the query
– fa06
Nov 13 '18 at 12:18
add a comment |
You can use correlated subquery
DEMO
select * from
(select account_id, count(room_id) as cnt, room_id
from bookings
group by account_id, room_id
)A inner join rooms on A.room_id=rooms.room_id
where cnt in (select max(cnt) from
(select account_id, count(room_id) as cnt, room_id
from bookings
group by account_id, room_id
)B where A.account_id=B.account_id)
In the demo provided this still shows more than one instance of eachaccount_id
– Imran
Nov 13 '18 at 12:14
it's because of your sample data - you can see that for 124 you've entered 1, 4, 5 room - so the room no is unique here, so for each room the count is one - in this case which one you want to pick
– fa06
Nov 13 '18 at 12:15
@fa06 whenever I tries to access the demo it redirects to the homepage of dbfiddle
– Sanal Sunny
Nov 13 '18 at 12:17
@SanalSunny - db-fiddle.com/f/hNedhkY8AHSYcVEVmrSV8q/0 - you need to exeute the query
– fa06
Nov 13 '18 at 12:18
add a comment |
You can use correlated subquery
DEMO
select * from
(select account_id, count(room_id) as cnt, room_id
from bookings
group by account_id, room_id
)A inner join rooms on A.room_id=rooms.room_id
where cnt in (select max(cnt) from
(select account_id, count(room_id) as cnt, room_id
from bookings
group by account_id, room_id
)B where A.account_id=B.account_id)
You can use correlated subquery
DEMO
select * from
(select account_id, count(room_id) as cnt, room_id
from bookings
group by account_id, room_id
)A inner join rooms on A.room_id=rooms.room_id
where cnt in (select max(cnt) from
(select account_id, count(room_id) as cnt, room_id
from bookings
group by account_id, room_id
)B where A.account_id=B.account_id)
edited Nov 13 '18 at 12:15
answered Nov 13 '18 at 12:07
fa06fa06
11.7k2917
11.7k2917
In the demo provided this still shows more than one instance of eachaccount_id
– Imran
Nov 13 '18 at 12:14
it's because of your sample data - you can see that for 124 you've entered 1, 4, 5 room - so the room no is unique here, so for each room the count is one - in this case which one you want to pick
– fa06
Nov 13 '18 at 12:15
@fa06 whenever I tries to access the demo it redirects to the homepage of dbfiddle
– Sanal Sunny
Nov 13 '18 at 12:17
@SanalSunny - db-fiddle.com/f/hNedhkY8AHSYcVEVmrSV8q/0 - you need to exeute the query
– fa06
Nov 13 '18 at 12:18
add a comment |
In the demo provided this still shows more than one instance of eachaccount_id
– Imran
Nov 13 '18 at 12:14
it's because of your sample data - you can see that for 124 you've entered 1, 4, 5 room - so the room no is unique here, so for each room the count is one - in this case which one you want to pick
– fa06
Nov 13 '18 at 12:15
@fa06 whenever I tries to access the demo it redirects to the homepage of dbfiddle
– Sanal Sunny
Nov 13 '18 at 12:17
@SanalSunny - db-fiddle.com/f/hNedhkY8AHSYcVEVmrSV8q/0 - you need to exeute the query
– fa06
Nov 13 '18 at 12:18
In the demo provided this still shows more than one instance of each
account_id
– Imran
Nov 13 '18 at 12:14
In the demo provided this still shows more than one instance of each
account_id
– Imran
Nov 13 '18 at 12:14
it's because of your sample data - you can see that for 124 you've entered 1, 4, 5 room - so the room no is unique here, so for each room the count is one - in this case which one you want to pick
– fa06
Nov 13 '18 at 12:15
it's because of your sample data - you can see that for 124 you've entered 1, 4, 5 room - so the room no is unique here, so for each room the count is one - in this case which one you want to pick
– fa06
Nov 13 '18 at 12:15
@fa06 whenever I tries to access the demo it redirects to the homepage of dbfiddle
– Sanal Sunny
Nov 13 '18 at 12:17
@fa06 whenever I tries to access the demo it redirects to the homepage of dbfiddle
– Sanal Sunny
Nov 13 '18 at 12:17
@SanalSunny - db-fiddle.com/f/hNedhkY8AHSYcVEVmrSV8q/0 - you need to exeute the query
– fa06
Nov 13 '18 at 12:18
@SanalSunny - db-fiddle.com/f/hNedhkY8AHSYcVEVmrSV8q/0 - you need to exeute the query
– fa06
Nov 13 '18 at 12:18
add a comment |
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1
Sample data and desired results in the question would clarify what you want. I'm not sure why you set up a MySQL fiddle for a question tagged tsql.
– Gordon Linoff
Nov 13 '18 at 11:58
I have updated the question to include the desired output, tsql wasn't supported in the tool used but the question is for tsql not mysql hence the tags used.
– Imran
Nov 13 '18 at 12:07