CODEWITHSUNDEEP
sqlcountgroup-by
Stavros
Stavros

Reputation: 6140

How to use count and group by at the same select statement

I have an SQL SELECT query that also uses a GROUP BY, I want to count all the records after the GROUP BY clause filtered the resultset.

Is there any way to do this directly with SQL? For example, if I have the table users and want to select the different towns and the total number of users:

SELECT `town`, COUNT(*)
FROM `user`
GROUP BY  `town`;

I want to have a column with all the towns and another with the number of users in all rows.

An example of the result for having 3 towns and 58 users in total is:

Town Count
Copenhagen 58
New York 58
Athens 58

Upvotes: 305

Views: 898973

Answers (11)

milkovsky
milkovsky

Reputation: 8862

You can use COUNT(DISTINCT ...) :

SELECT COUNT(DISTINCT town) 
FROM user

Upvotes: 195

Oded
Oded

Reputation: 499302

This will do what you want (list of towns, with the number of users in each):

SELECT `town`, COUNT(`town`)
FROM `user`
GROUP BY `town`;

You can use most aggregate functions when using a GROUP BY statement (COUNT, MAX, COUNT DISTINCT etc.)

Update: You can declare a variable for the number of users and save the result there, and then SELECT the value of the variable:

DECLARE @numOfUsers INT
SET @numOfUsers = SELECT COUNT(*) FROM `user`;

SELECT DISTINCT `town`, @numOfUsers FROM `user`;

Upvotes: 350

Rick James
Rick James

Reputation: 142518

Ten non-deleted answers; most do not do what the user asked for. Most Answers mis-read the question as thinking that there are 58 users in each town instead of 58 in total. Even the few that are correct are not optimal.

mysql> flush status;
Query OK, 0 rows affected (0.00 sec)

SELECT  province, total_cities
    FROM       ( SELECT  DISTINCT province  FROM  canada ) AS provinces
    CROSS JOIN ( SELECT  COUNT(*) total_cities  FROM  canada ) AS tot;
+---------------------------+--------------+
| province                  | total_cities |
+---------------------------+--------------+
| Alberta                   |         5484 |
| British Columbia          |         5484 |
| Manitoba                  |         5484 |
| New Brunswick             |         5484 |
| Newfoundland and Labrador |         5484 |
| Northwest Territories     |         5484 |
| Nova Scotia               |         5484 |
| Nunavut                   |         5484 |
| Ontario                   |         5484 |
| Prince Edward Island      |         5484 |
| Quebec                    |         5484 |
| Saskatchewan              |         5484 |
| Yukon                     |         5484 |
+---------------------------+--------------+
13 rows in set (0.01 sec)

SHOW session status LIKE 'Handler%';

+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| Handler_commit             | 1     |
| Handler_delete             | 0     |
| Handler_discover           | 0     |
| Handler_external_lock      | 4     |
| Handler_mrr_init           | 0     |
| Handler_prepare            | 0     |
| Handler_read_first         | 3     |
| Handler_read_key           | 16    |
| Handler_read_last          | 1     |
| Handler_read_next          | 5484  |  -- One table scan to get COUNT(*)
| Handler_read_prev          | 0     |
| Handler_read_rnd           | 0     |
| Handler_read_rnd_next      | 15    |
| Handler_rollback           | 0     |
| Handler_savepoint          | 0     |
| Handler_savepoint_rollback | 0     |
| Handler_update             | 0     |
| Handler_write              | 14    |  -- leapfrog through index to find provinces  
+----------------------------+-------+

In the OP's context:

SELECT  town, total_users
    FROM       ( SELECT  DISTINCT town  FROM  canada ) AS towns
    CROSS JOIN ( SELECT  COUNT(*) total_users  FROM  canada ) AS tot;

Since there is only one row from tot, the CROSS JOIN is not as voluminous as it might otherwise be.

The usual pattern is COUNT(*) instead of COUNT(town). The latter implies checking town for being not null, which is unnecessary in this context.

Upvotes: 13

Prakash
Prakash

Reputation: 100

if You Want to use Select All Query With Count Option, try this...

 select a.*, (Select count(b.name) from table_name as b where Condition) as totCount from table_name  as a where where Condition

Upvotes: 1

ZhenYu Wang
ZhenYu Wang

Reputation: 1117

The other way is:

/* Number of rows in a derived table called d1. */
select count(*) from
(
  /* Number of times each town appears in user. */
  select town, count(*)
  from user
  group by town
) d1

Upvotes: 49

Marcus
Marcus

Reputation: 29

I know this is an old post, in SQL Server:

select  isnull(town,'TOTAL') Town, count(*) cnt
from    user
group by town WITH ROLLUP

Town         cnt
Copenhagen   58
NewYork      58
Athens       58
TOTAL        174

Upvotes: 2

balajibran
balajibran

Reputation: 72

Try the following code:

select ccode, count(empno) 
from company_details 
group by ccode;

Upvotes: 0

Violendy Firdaus
Violendy Firdaus

Reputation: 19

If you want to select town and total user count, you can use this query below:

SELECT Town, (SELECT Count(*) FROM User) `Count` FROM user GROUP BY Town;

Upvotes: 1

Jur P
Jur P

Reputation: 99

You can use DISTINCT inside the COUNT like what milkovsky said

in my case:

select COUNT(distinct user_id) from answers_votes where answer_id in (694,695);

This will pull the count of answer votes considered the same user_id as one count

Upvotes: 4

Renato Probst
Renato Probst

Reputation: 6054

If you want to order by count (sound simple but i can`t found an answer on stack of how to do that) you can do:

        SELECT town, count(town) as total FROM user
        GROUP BY town ORDER BY total DESC

Upvotes: 4

Tommi
Tommi

Reputation: 8608

With Oracle you could use analytic functions:

select town, count(town), sum(count(town)) over () total_count from user
group by town

Your other options is to use a subquery:

select town, count(town), (select count(town) from user) as total_count from user
group by town

Upvotes: 6

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