SQL Server/T-SQL Tutorial/Aggregate Functions/AVG — различия между версиями
Admin (обсуждение | вклад) м (1 версия) |
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Текущая версия на 10:23, 26 мая 2010
Содержание
- 1 adds the WHERE statement to calculate the average
- 2 A summary query that uses the COUNT, AVG, and SUM functions
- 3 AVG calculates the average for selected records of numeric data in a column or the average for DISTINCT (unique) values of the selected records.
- 4 CAST(AVG(dec1) AS dec(5,2))
- 5 Selecting titles that sell more than the average.
- 6 Using DISTINCT in Aggregate Functions
adds the WHERE statement to calculate the average
6> CREATE TABLE CD (
7> CD_ID integer NOT NULL PRIMARY KEY,
8> CD_Title varchar(40),
9> Composer_ID integer NOT NULL,
10> Classif_ID integer NOT NULL,
11> SalesPrice money,
12> AverageCost money)
13> GO
1> INSERT into CD VALUES(2000,"John",100,1,16.99,6.99)
2> INSERT into CD VALUES(2001,"Chicago 16",107,1,14.99,5.99)
3> INSERT into CD VALUES(2002,"Chicago 17",107,1,14.99,5.99)
4> INSERT into CD VALUES(2003,"Chicago 18",107,1,14.99,5.99)
5> INSERT into CD VALUES(2004,"Greatest Hits",107,1,16.99,7.99)
6> INSERT into CD VALUES(2005,"Midnight",101,3,14.99,5.99)
7> INSERT into CD VALUES(2006,"Mode",115,3,14.99,5.99)
8> INSERT into CD VALUES(2007,"Ultra",115,3,15.99,5.99)
9> INSERT into CD VALUES(2008,"Mindcrime",102,4,14.99,5.99)
10> INSERT into CD VALUES(2009,"Empire",102,4,14.99,5.99)
11> INSERT into CD VALUES(2010,"Land",102,4,12.99,4.99)
12> INSERT into CD VALUES(2011,"Night",103,4,11.99,3.99)
13> INSERT into CD VALUES(2012,"Pyromania",103,4,14.99,5.99)
14> INSERT into CD VALUES(2013,"Hysteria",103,4,14.99,5.99)
15> INSERT into CD VALUES(2014,"Hits",103,4,13.99,4.99)
16> INSERT into CD VALUES(2015,"Hits 2",104,2,15.99,6.99)
17> INSERT into CD VALUES(2016,"Greatest",105,2,14.99,5.99)
18> INSERT into CD VALUES(2017,"Hits 3",106,1,13.99,5.99)
19> INSERT into CD VALUES(2018,"Deep",108,1,12.99,2.99)
20> INSERT into CD VALUES(2019,"Turning",109,1,14.99,5.99)
21> INSERT into CD VALUES(2020,"TheHits",109,1,16.99,7.99)
22> INSERT into CD VALUES(2021,"Cars",110,1,9.99,3.99)
23> INSERT into CD VALUES(2022,"Anthology",110,1,25.99,11.99)
24> INSERT into CD VALUES(2023,"City",110,1,14.99,5.99)
25> INSERT into CD VALUES(2024,"Rick",111,1,11.99,2.99)
26> INSERT into CD VALUES(2025,"Live",112,1,19.99,8.99)
27> INSERT into CD VALUES(2026,"Pat",113,1,16.99,6.99)
28> INSERT into CD VALUES(2027,"Big",114,1,14.99,5.99)
29> INSERT into CD VALUES(2028,"Hurting",114,1,11.99,3.99)
30> INSERT into CD VALUES(2029,"Vol 1",116,1,9.99,2.99)
31> INSERT into CD VALUES(2030,"Vol 2",116,1,9.99,2.99)
32> GO
(1 rows affected)
(1 rows affected)
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1>
2> SELECT AVG(SalesPrice),AVG(AverageCost) from CD WHERE Classif_ID = 1
3> GO
--------------------- ---------------------
14.9900 5.9373
(1 rows affected)
1>
2> drop table CD;
3> GO
A summary query that uses the COUNT, AVG, and SUM functions
3>
4> create table Billings (
5> BankerID INTEGER,
6> BillingNumber INTEGER,
7> BillingDate datetime,
8> BillingTotal INTEGER,
9> TermsID INTEGER,
10> BillingDueDate datetime ,
11> PaymentTotal INTEGER,
12> CreditTotal INTEGER
13>
14> );
15> GO
1>
2> INSERT INTO Billings VALUES (1, 1, "2005-01-22", 165, 1,"2005-04-22",123,321);
3> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (2, 2, "2001-02-21", 165, 1,"2002-02-22",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (3, 3, "2003-05-02", 165, 1,"2005-04-12",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (4, 4, "1999-03-12", 165, 1,"2005-04-18",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (5, 5, "2000-04-23", 165, 1,"2005-04-17",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (6, 6, "2001-06-14", 165, 1,"2005-04-18",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (7, 7, "2002-07-15", 165, 1,"2005-04-19",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (8, 8, "2003-08-16", 165, 1,"2005-04-20",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (9, 9, "2004-09-17", 165, 1,"2005-04-21",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (0, 0, "2005-10-18", 165, 1,"2005-04-22",123,321);
2> GO
(1 rows affected)
1>
2>
3> SELECT "After 1/1/2002" AS SelectionDate, COUNT(*) AS NumberOfBillings,
4> AVG(BillingTotal) AS AverageBillingAmount,
5> SUM(BillingTotal) AS TotalBillingAmount
6> FROM Billings
7> WHERE BillingDate > "2002-01-01"
8> GO
SelectionDate NumberOfBillings AverageBillingAmount TotalBillingAmount
-------------- ---------------- -------------------- ------------------
After 1/1/2002 6 165 990
(1 rows affected)
1>
2> drop table Billings;
3> GO
AVG calculates the average for selected records of numeric data in a column or the average for DISTINCT (unique) values of the selected records.
All NULL values are ignored in the computation for the total and the record count.
computes the average on the rows selected by the query, or the DISTINCT rows.
The return datatype is the same datatype as the column being averaged.
Only the numeric datatypes can be used with the AVG function.
6> CREATE TABLE sales(
7> stor_id char(4) NOT NULL,
8> ord_num varchar(20) NOT NULL,
9> ord_date datetime NOT NULL,
10> qty smallint NOT NULL,
11> payterms varchar(12) NOT NULL,
12> title_id varchar(80)
13> )
14> GO
1> insert sales values("1", "QA7442.3", "09/13/94", 75, "ON Billing","1")
2> insert sales values("2", "D4482", "09/14/94", 10, "Net 60", "1")
3> insert sales values("3", "N914008", "09/14/94", 20, "Net 30", "2")
4> insert sales values("4", "N914014", "09/14/94", 25, "Net 30", "3")
5> insert sales values("5", "423LL922", "09/14/94", 15, "ON Billing","3")
6> insert sales values("6", "423LL930", "09/14/94", 10, "ON Billing","2")
7> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
1>
2>
3> select avg(qty) from sales;
4> GO
-----------
25
(1 rows affected)
1>
2> drop table sales;
3>
4> GO
1>
CAST(AVG(dec1) AS dec(5,2))
6> CREATE TABLE T (
7> int1 int,
8> bit1 bit,
9> varchar1 varchar(3),
10> dec1 dec(5,2),
11> cmp1 AS (int1 + bit1)
12> )
13> GO
1>
2> INSERT T (int1, bit1) VALUES (1, 0)
3> INSERT T (int1, varchar1) VALUES (2, "abc")
4> INSERT T (int1, dec1) VALUES (3, 5.25)
5> INSERT T (bit1, dec1) VALUES (1, 9.75)
6> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
1> SELECT CAST(AVG(dec1) AS dec(5,2)) "Avg of dec1"
2> FROM T
3> WHERE dec1 IS NOT NULL
4> GO
Avg of dec1
-----------
7.50
(1 rows affected)
1> drop table t;
2> GO
1>
2>
Selecting titles that sell more than the average.
3>
4>
5> CREATE TABLE titles(
6> title_id varchar(20),
7> title varchar(80) NOT NULL,
8> type char(12) NOT NULL,
9> pub_id char(4) NULL,
10> price money NULL,
11> advance money NULL,
12> royalty int NULL,
13> ytd_sales int NULL,
14> notes varchar(200) NULL,
15> pubdate datetime NOT NULL
16> )
17> GO
1>
2> insert titles values ("1", "Secrets", "popular_comp", "1389", $20.00, $8000.00, 10, 4095,"Note 1","06/12/94")
3> insert titles values ("2", "The", "business", "1389", $19.99, $5000.00, 10, 4095,"Note 2","06/12/91")
4> insert titles values ("3", "Emotional", "psychology", "0736", $7.99, $4000.00, 10, 3336,"Note 3","06/12/91")
5> insert titles values ("4", "Prolonged", "psychology", "0736", $19.99, $2000.00, 10, 4072,"Note 4","06/12/91")
6> insert titles values ("5", "With", "business", "1389", $11.95, $5000.00, 10, 3876,"Note 5","06/09/91")
7> insert titles values ("6", "Valley", "mod_cook", "0877", $19.99, $0.00, 12, 2032,"Note 6","06/09/91")
8> insert titles values ("7", "Any?", "trad_cook", "0877", $14.99, $8000.00, 10, 4095,"Note 7","06/12/91")
9> insert titles values ("8", "Fifty", "trad_cook", "0877", $11.95, $4000.00, 14, 1509,"Note 8","06/12/91")
10> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
1>
2> CREATE TABLE sales(
3> stor_id char(4) NOT NULL,
4> ord_num varchar(20) NOT NULL,
5> ord_date datetime NOT NULL,
6> qty smallint NOT NULL,
7> payterms varchar(12) NOT NULL,
8> title_id varchar(80)
9> )
10> GO
1> insert sales values("1", "QA7442.3", "09/13/94", 75, "ON Billing","1")
2> insert sales values("2", "D4482", "09/14/94", 10, "Net 60", "1")
3> insert sales values("3", "N914008", "09/14/94", 20, "Net 30", "2")
4> insert sales values("4", "N914014", "09/14/94", 25, "Net 30", "3")
5> insert sales values("5", "423LL922", "09/14/94", 15, "ON Billing","3")
6> insert sales values("6", "423LL930", "09/14/94", 10, "ON Billing","2")
7> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
1>
2> SELECT titles.title, titles.price
3> FROM titles JOIN sales ON sales.title_id = titles.title_id
4> WHERE sales.qty >
5> (SELECT AVG(qty)
6> FROM sales)
7> GO
title price
-------------------------------------------------------------------------------- ---------------------
Secrets 20.0000
(1 rows affected)
1>
2> drop table sales;
3> drop table titles;
4> GO
Using DISTINCT in Aggregate Functions
3>
4> CREATE TABLE employee(
5> id INTEGER NOT NULL PRIMARY KEY,
6> first_name VARCHAR(10),
7> last_name VARCHAR(10),
8> salary DECIMAL(10,2),
9> start_Date DATETIME,
10> region VARCHAR(10),
11> city VARCHAR(20)
12> );
13> GO
1> INSERT INTO employee VALUES (1, "Jason" , "Martin", 5890,"2005-03-22","North","Vancouver");
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (2, "Alison", "Mathews",4789,"2003-07-21","South","Utown");
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (3, "James" , "Smith", 6678,"2001-12-01","North","Paris");
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (4, "Celia" , "Rice", 5567,"2006-03-03","South","London");
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (5, "Robert", "Black", 4467,"2004-07-02","East","Newton");
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (6, "Linda" , "Green" , 6456,"2002-05-19","East","Calgary");
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (7, "David" , "Larry", 5345,"2008-03-18","West","New York");
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (8, "James" , "Cat", 4234,"2007-07-17","West","Regina");
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (9, "Joan" , "Act", 6123,"2001-04-16","North","Toronto");
2> GO
(1 rows affected)
1>
2> select * from employee;
3> GO
id first_name last_name salary start_Date region city
----------- ---------- ---------- ------------ ----------------------- ---------- --------------------
1 Jason Martin 5890.00 2005-03-22 00:00:00.000 North Vancouver
2 Alison Mathews 4789.00 2003-07-21 00:00:00.000 South Utown
3 James Smith 6678.00 2001-12-01 00:00:00.000 North Paris
4 Celia Rice 5567.00 2006-03-03 00:00:00.000 South London
5 Robert Black 4467.00 2004-07-02 00:00:00.000 East Newton
6 Linda Green 6456.00 2002-05-19 00:00:00.000 East Calgary
7 David Larry 5345.00 2008-03-18 00:00:00.000 West New York
8 James Cat 4234.00 2007-07-17 00:00:00.000 West Regina
9 Joan Act 6123.00 2001-04-16 00:00:00.000 North Toronto
(9 rows affected)
1>
2>
3> SELECT AVG(DISTINCT salary)
4> FROM employee;
5> GO
----------------------------------------
5505.444444
(1 rows affected)
1>
2>
3>
4>
5> drop table employee;
6> GO