MySQL Tutorial/Aggregate Functions/Introduction

Aggregate Functions

Aggregate functions perform a mathematical operation on a column.

MySQL implements the following aggregate functions:

1. COUNT(),
2. COUNT(DISTINCT),
3. MAX(),
4. MIN(),
5. AVG(),
6. SUM(), and
7. STD().

16. 1. Introduction 16. 1. 1. Aggregate Functions 16. 1. 2. <A href="/Tutorial/MySQL/0320__Aggregate-Functions/Usetwoaggregatefunctionsinaselectstatement.htm">Use two aggregate functions in a select statement</a> 16. 1. 3. <A href="/Tutorial/MySQL/0320__Aggregate-Functions/Useaggregatefunctionwithgroupbyclause.htm">Use aggregate function with group by clause</a>

Use aggregate function with group by clause

   <source lang="sql">

mysql> mysql> mysql> CREATE TABLE Topic(

   ->    TopicID     SMALLINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
   ->    Name        VARCHAR(50) NOT NULL,
   ->    InStock     SMALLINT UNSIGNED NOT NULL,
   ->    OnOrder     SMALLINT UNSIGNED NOT NULL,
   ->    Reserved    SMALLINT UNSIGNED NOT NULL,
   ->    Department  ENUM("Classical", "Popular") NOT NULL,
   ->    Category    VARCHAR(20) NOT NULL,
   ->    RowUpdate   TIMESTAMP NOT NULL
   -> );

Query OK, 0 rows affected (0.02 sec) mysql> mysql> mysql> INSERT INTO Topic (Name, InStock, OnOrder, Reserved, Department, Category) VALUES

   ->                   ("Java",          10,      5,       3,        "Popular",    "Rock"),
   ->                   ("JavaScript",    10,      5,       3,        "Classical",  "Opera"),
   ->                   ("C Sharp",       17,      4,       1,        "Popular",    "Jazz"),
   ->                   ("C",             9,       4,       2,        "Classical",  "Dance"),
   ->                   ("C++",           24,      2,       5,        "Classical",  "General"),
   ->                   ("Perl",          16,      6,       8,        "Classical",  "Vocal"),
   ->                   ("Python",        2,       25,      6,        "Popular",    "Blues"),
   ->                   ("Php",           32,      3,       10,       "Popular",    "Jazz"),
   ->                   ("ASP.net",       12,      15,      13,       "Popular",    "Country"),
   ->                   ("VB.net",        5,       20,      10,       "Popular",    "New Age"),
   ->                   ("VC.net",        24,      11,      14,       "Popular",    "New Age"),
   ->                   ("UML",           42,      17,      17,       "Classical",  "General"),
   ->                   ("www.sqle.ru",25,      44,      28,       "Classical",  "Dance"),
   ->                   ("Oracle",        32,      15,      12,       "Classical",  "General"),
   ->                   ("Pl/SQL",        20,      10,      5,        "Classical",  "Opera"),
   ->                   ("Sql Server",    23,      12,      8,        "Classical",  "General");

Query OK, 16 rows affected (0.02 sec) Records: 16 Duplicates: 0 Warnings: 0 mysql> mysql> select * from Topic; +---------+----------------+---------+---------+----------+------------+----------+---------------------+ | TopicID | Name | InStock | OnOrder | Reserved | Department | Category | RowUpdate | +---------+----------------+---------+---------+----------+------------+----------+---------------------+ | 1 | Java | 10 | 5 | 3 | Popular | Rock | 2007-07-23 19:09:42 | | 2 | JavaScript | 10 | 5 | 3 | Classical | Opera | 2007-07-23 19:09:42 | | 3 | C Sharp | 17 | 4 | 1 | Popular | Jazz | 2007-07-23 19:09:42 | | 4 | C | 9 | 4 | 2 | Classical | Dance | 2007-07-23 19:09:42 | | 5 | C++ | 24 | 2 | 5 | Classical | General | 2007-07-23 19:09:42 | | 6 | Perl | 16 | 6 | 8 | Classical | Vocal | 2007-07-23 19:09:42 | | 7 | Python | 2 | 25 | 6 | Popular | Blues | 2007-07-23 19:09:42 | | 8 | Php | 32 | 3 | 10 | Popular | Jazz | 2007-07-23 19:09:42 | | 9 | ASP.net | 12 | 15 | 13 | Popular | Country | 2007-07-23 19:09:42 | | 10 | VB.net | 5 | 20 | 10 | Popular | New Age | 2007-07-23 19:09:42 | | 11 | VC.net | 24 | 11 | 14 | Popular | New Age | 2007-07-23 19:09:42 | | 12 | UML | 42 | 17 | 17 | Classical | General | 2007-07-23 19:09:42 | | 13 | www.sqle.ru | 25 | 44 | 28 | Classical | Dance | 2007-07-23 19:09:42 | | 14 | Oracle | 32 | 15 | 12 | Classical | General | 2007-07-23 19:09:42 | | 15 | Pl/SQL | 20 | 10 | 5 | Classical | Opera | 2007-07-23 19:09:42 | | 16 | Sql Server | 23 | 12 | 8 | Classical | General | 2007-07-23 19:09:42 | +---------+----------------+---------+---------+----------+------------+----------+---------------------+ 16 rows in set (0.00 sec) mysql> mysql> mysql> SELECT Category, COUNT(*) AS Total

   -> FROM Topic
   -> WHERE Department="Popular"
   -> GROUP BY Category;

+----------+-------+ | Category | Total | +----------+-------+ | Blues | 1 | | Country | 1 | | Jazz | 2 | | New Age | 2 | | Rock | 1 | +----------+-------+ 5 rows in set (0.02 sec) mysql> mysql> drop table Topic; Query OK, 0 rows affected (0.02 sec)</source>

Use two aggregate functions in a select statement

   <source lang="sql">

mysql> mysql> mysql> mysql> CREATE TABLE Employee(

   ->     id            int,
   ->     first_name    VARCHAR(15),
   ->     last_name     VARCHAR(15),
   ->     start_date    DATE,
   ->     end_date      DATE,
   ->     salary        FLOAT(8,2),
   ->     city          VARCHAR(10),
   ->     description   VARCHAR(15)
   -> );

Query OK, 0 rows affected (0.05 sec) mysql> mysql> mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)

   ->              values (1,"Jason",    "Martin",  "19960725",  "20060725", 1234.56, "Toronto",  "Programmer");

Query OK, 1 row affected (0.01 sec) mysql> mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)

   ->               values(2,"Alison",   "Mathews",  "19760321", "19860221", 6661.78, "Vancouver","Tester");

Query OK, 1 row affected (0.00 sec) mysql> mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)

   ->               values(3,"James",    "Smith",    "19781212", "19900315", 6544.78, "Vancouver","Tester");

Query OK, 1 row affected (0.00 sec) mysql> mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)

   ->               values(4,"Celia",    "Rice",     "19821024", "19990421", 2344.78, "Vancouver","Manager");

Query OK, 1 row affected (0.00 sec) mysql> mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)

   ->               values(5,"Robert",   "Black",    "19840115", "19980808", 2334.78, "Vancouver","Tester");

Query OK, 1 row affected (0.00 sec) mysql> mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)

   ->               values(6,"Linda",    "Green",    "19870730", "19960104", 4322.78,"New York",  "Tester");

Query OK, 1 row affected (0.00 sec) mysql> mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)

   ->               values(7,"David",    "Larry",    "19901231", "19980212", 7897.78,"New York",  "Manager");

Query OK, 1 row affected (0.00 sec) mysql> mysql> insert into Employee(id,first_name, last_name, start_date, end_Date, salary, City, Description)

   ->               values(8,"James",    "Cat",     "19960917",  "20020415", 1232.78,"Vancouver", "Tester");

Query OK, 1 row affected (0.00 sec) mysql> mysql> select * from Employee; +------+------------+-----------+------------+------------+---------+-----------+-------------+ | id | first_name | last_name | start_date | end_date | salary | city | description | +------+------------+-----------+------------+------------+---------+-----------+-------------+ | 1 | Jason | Martin | 1996-07-25 | 2006-07-25 | 1234.56 | Toronto | Programmer | | 2 | Alison | Mathews | 1976-03-21 | 1986-02-21 | 6661.78 | Vancouver | Tester | | 3 | James | Smith | 1978-12-12 | 1990-03-15 | 6544.78 | Vancouver | Tester | | 4 | Celia | Rice | 1982-10-24 | 1999-04-21 | 2344.78 | Vancouver | Manager | | 5 | Robert | Black | 1984-01-15 | 1998-08-08 | 2334.78 | Vancouver | Tester | | 6 | Linda | Green | 1987-07-30 | 1996-01-04 | 4322.78 | New York | Tester | | 7 | David | Larry | 1990-12-31 | 1998-02-12 | 7897.78 | New York | Manager | | 8 | James | Cat | 1996-09-17 | 2002-04-15 | 1232.78 | Vancouver | Tester | +------+------------+-----------+------------+------------+---------+-----------+-------------+ 8 rows in set (0.00 sec) mysql> mysql> mysql> mysql> SELECT count(*), SUM(salary)

   -> FROM employee;

+----------+-------------+ | count(*) | SUM(salary) | +----------+-------------+ | 8 | 32574.02 | +----------+-------------+ 1 row in set (0.00 sec) mysql> mysql> mysql> mysql> mysql> drop table Employee; Query OK, 0 rows affected (0.00 sec) mysql></source>