SQL Server/T-SQL Tutorial/Transact SQL/Variable Select — различия между версиями
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Версия 13:46, 26 мая 2010
Содержание
- 1 An alternate syntax for setting a variable"s value in a select list
- 2 Assignment with a Subquery
- 3 Creating a Comma Delimited List using SELECT
- 4 Example of a Variable Not Updated Due to No Rows Being Returned
- 5 multiple variables can be assigned values in a single operation.
- 6 Syntax for Variable Assignment with the SELECT Statement
- 7 Use select to output a variable
- 8 Using SELECT to Assign Variables
An alternate syntax for setting a variable"s value in a select list
SELECT @variable_name = column_specification
Assignment with a Subquery
4>
5>
6> CREATE TABLE employee(
7> id INTEGER NOT NULL PRIMARY KEY,
8> first_name VARCHAR(10),
9> last_name VARCHAR(10),
10> salary DECIMAL(10,2),
11> start_Date DATETIME,
12> region VARCHAR(10),
13> city VARCHAR(20),
14> managerid INTEGER
15> );
16> GO
1> INSERT INTO employee VALUES (1, "Jason" , "Martin", 5890,"2005-03-22","North","Vancouver",3);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (2, "Alison", "Mathews",4789,"2003-07-21","South","Utown",4);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (3, "James" , "Smith", 6678,"2001-12-01","North","Paris",5);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (4, "Celia" , "Rice", 5567,"2006-03-03","South","London",6);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (5, "Robert", "Black", 4467,"2004-07-02","East","Newton",7);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (6, "Linda" , "Green" , 6456,"2002-05-19","East","Calgary",8);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (7, "David" , "Larry", 5345,"2008-03-18","West","New York",9);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (8, "James" , "Cat", 4234,"2007-07-17","West","Regina",9);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (9, "Joan" , "Act", 6123,"2001-04-16","North","Toronto",10);
2> GO
(1 rows affected)
1>
2> select * from employee;
3> GO
id first_name last_name salary start_Date region city managerid
----------- ---------- ---------- ------------ ----------------------- ---------- -------------------- -----------
1 Jason Martin 5890.00 2005-03-22 00:00:00.000 North Vancouver 3
2 Alison Mathews 4789.00 2003-07-21 00:00:00.000 South Utown 4
3 James Smith 6678.00 2001-12-01 00:00:00.000 North Paris 5
4 Celia Rice 5567.00 2006-03-03 00:00:00.000 South London 6
5 Robert Black 4467.00 2004-07-02 00:00:00.000 East Newton 7
6 Linda Green 6456.00 2002-05-19 00:00:00.000 East Calgary 8
7 David Larry 5345.00 2008-03-18 00:00:00.000 West New York 9
8 James Cat 4234.00 2007-07-17 00:00:00.000 West Regina 9
9 Joan Act 6123.00 2001-04-16 00:00:00.000 North Toronto 10
(9 rows affected)
1>
2> DECLARE
3> @ID int
4> SELECT
5> @ID = 0
6> SELECT
7> @ID =
8> (
9> SELECT
10> ID
11> FROM
12> Employee
13> WHERE
14> ID = 1
15> )
16> SELECT
17> @ID
18>
19>
20>
21> drop table employee;
22> GO
-----------
1
(1 rows affected)
1>
Creating a Comma Delimited List using SELECT
5> CREATE TABLE employee(
6> id INTEGER NOT NULL PRIMARY KEY,
7> first_name VARCHAR(10),
8> last_name VARCHAR(10),
9> salary DECIMAL(10,2),
10> start_Date DATETIME,
11> region VARCHAR(10),
12> city VARCHAR(20)
13> );
14> GO
1> INSERT INTO employee VALUES (1, "Jason" , "Martin", 5890,"2005-03-22","North","Vancouver");
2> GO
(1 rows affected)
1>
2>
3> INSERT INTO employee VALUES (2, "Alison", "Mathews",4789,"2003-07-21","South","Utown");
4> GO
(1 rows affected)
1>
2>
3> INSERT INTO employee VALUES (3, "James" , "Smith", 6678,"2001-12-01","North","Paris");
4> GO
(1 rows affected)
1>
2>
3> INSERT INTO employee VALUES (4, "Celia" , "Rice", 5567,"2006-03-03","South","London");
4> GO
(1 rows affected)
1>
2>
3> INSERT INTO employee VALUES (5, "Robert", "Black", 4467,"2004-07-02","East","Newton");
4> GO
(1 rows affected)
1>
2>
3> INSERT INTO employee VALUES (6, "Linda" , "Green" , 6456,"2002-05-19","East","Calgary");
4> GO
(1 rows affected)
1>
2>
3> INSERT INTO employee VALUES (7, "David" , "Larry", 5345,"2008-03-18","West","New York");
4> GO
(1 rows affected)
1>
2>
3> INSERT INTO employee VALUES (8, "James" , "Cat", 4234,"2007-07-17","West","Regina");
4> GO
(1 rows affected)
1>
2>
3> INSERT INTO employee VALUES (9, "Joan" , "Act", 6123,"2001-04-16","North","Toronto");
4> GO
(1 rows affected)
1>
2>
3>
4> select * from employee;
5> 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>
4> DECLARE @Shifts varchar(20)
5> SET @Shifts = ""
6> SELECT @Shifts = @Shifts + s.first_Name + ","
7> FROM employee s
8> ORDER BY s.start_Date;
9>
10> SELECT @Shifts;
11> GO
--------------------
Joan,James,Linda,Ali
(1 rows affected)
1>
2>
3>
4> drop table employee;
5> GO
Example of a Variable Not Updated Due to No Rows Being Returned
9> CREATE TABLE employee(
10> id INTEGER NOT NULL PRIMARY KEY,
11> first_name VARCHAR(10),
12> last_name VARCHAR(10),
13> salary DECIMAL(10,2),
14> start_Date DATETIME,
15> region VARCHAR(10),
16> city VARCHAR(20),
17> managerid INTEGER
18> );
19> GO
1> INSERT INTO employee VALUES (1, "Jason" , "Martin", 5890,"2005-03-22","North","Vancouver",3);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (2, "Alison", "Mathews",4789,"2003-07-21","South","Utown",4);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (3, "James" , "Smith", 6678,"2001-12-01","North","Paris",5);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (4, "Celia" , "Rice", 5567,"2006-03-03","South","London",6);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (5, "Robert", "Black", 4467,"2004-07-02","East","Newton",7);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (6, "Linda" , "Green" , 6456,"2002-05-19","East","Calgary",8);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (7, "David" , "Larry", 5345,"2008-03-18","West","New York",9);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (8, "James" , "Cat", 4234,"2007-07-17","West","Regina",9);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (9, "Joan" , "Act", 6123,"2001-04-16","North","Toronto",10);
2> GO
(1 rows affected)
1>
2> select * from employee;
3> GO
id first_name last_name salary start_Date region city managerid
----------- ---------- ---------- ------------ ----------------------- ---------- -------------------- -----------
1 Jason Martin 5890.00 2005-03-22 00:00:00.000 North Vancouver 3
2 Alison Mathews 4789.00 2003-07-21 00:00:00.000 South Utown 4
3 James Smith 6678.00 2001-12-01 00:00:00.000 North Paris 5
4 Celia Rice 5567.00 2006-03-03 00:00:00.000 South London 6
5 Robert Black 4467.00 2004-07-02 00:00:00.000 East Newton 7
6 Linda Green 6456.00 2002-05-19 00:00:00.000 East Calgary 8
7 David Larry 5345.00 2008-03-18 00:00:00.000 West New York 9
8 James Cat 4234.00 2007-07-17 00:00:00.000 West Regina 9
9 Joan Act 6123.00 2001-04-16 00:00:00.000 North Toronto 10
(9 rows affected)
1>
2>
3>
4> DECLARE
5> @ID int
6> SELECT
7> @ID = 0
8> SELECT
9> @ID = ID
10> FROM
11> Employee
12> WHERE
13> ID = 1
14> SELECT
15> @ID
16>
17>
18> drop table employee;
19> GO
-----------
1
(1 rows affected)
1>
multiple variables can be assigned values in a single operation.
6>
7> DECLARE @MyNumber1 Int, @MyNumber2 Int, @MyResult1 Int, @MyResult2 Int
8> SELECT @MyNumber1 = 144, @MyNumber2 = 121
9> -- Assign the function result to the variable:
10> SELECT @MyResult1 = SQRT(@MyNumber1), @MyResult2 = SQRT(@MyNumber2)
11> -- Return the variable value
12> SELECT @MyResult1, @MyResult2
13> GO
----------- -----------
12 11
(1 rows affected)
Syntax for Variable Assignment with the SELECT Statement
SELECT {@local_variable = expression } [,...n]
Use select to output a variable
3> CREATE TABLE authors(
4> au_id varchar(11),
5> au_lname varchar(40) NOT NULL,
6> au_fname varchar(20) NOT NULL,
7> phone char(12) NOT NULL DEFAULT ("UNKNOWN"),
8> address varchar(40) NULL,
9> city varchar(20) NULL,
10> state char(2) NULL,
11> zip char(5) NULL,
12> contract bit NOT NULL
13> )
14> GO
1> insert authors values("1", "Joe", "Abra", "111 111-1111", "6 St.", "Berkeley", "CA", "11111", 1)
2> insert authors values("2", "Jack", "Majo", "222 222-2222", "3 St.", "Oakland" , "CA", "22222", 1)
3> insert authors values("3", "Pink", "Cherry", "333 333-3333", "5 Ln.", "Vancouver", "BC", "33333", 1)
4> insert authors values("4", "Blue", "Albert", "444 444-4444", "7 Av.", "Vancouver", "BC", "44444", 1)
5> insert authors values("5", "Red", "Anne", "555 555-5555", "6 Av.", "Regina", "SK", "55555", 1)
6> insert authors values("6", "Black", "Michel", "666 666-6666", "3 Pl.", "Regina", "SK", "66666", 1)
7> insert authors values("7", "White", "Sylvia", "777 777-7777", "1 Pl.", "Rockville", "MD", "77777", 1)
8> insert authors values("8", "Yellow","Heather","888 888-8888", "3 Pu", "Vacaville", "CA", "88888", 0)
9> insert authors values("9", "Gold", "Dep", "999 999-9999", "5 Av.", "Oakland", "CA", "99999", 0)
10> insert authors values("10", "Siler", "Dean", "000 000-0000", "4 Av.", "Oakland", "CA", "00000", 1)
11> 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 rows affected)
(1 rows affected)
1>
2>
3> DECLARE @firstname varchar(20)
4> SELECT @firstname = au_fname
5> FROM authors
6> WHERE au_lname = "Greene"
7>
8> SELECT @firstname
9> SELECT @firstname = au_fname
10> FROM authors
11> WHERE au_lname = "Ben-Gan"
12> SELECT @firstname
13> GO
--------------------
NULL
(1 rows affected)
--------------------
NULL
(1 rows affected)
1>
2> drop table authors;
3> GO
Using SELECT to Assign Variables
3> DECLARE @MyNumber1 Int, @MyNumber2 Int, @MyResult1 Int, @MyResult2 Int
4> SELECT @MyNumber1 = 144, @MyNumber2 = 121
5>
6> SELECT @MyResult1 = SQRT(@MyNumber1), @MyResult2 = SQRT(@MyNumber2)
7>
8> SELECT @MyResult1, @MyResult2
9> GO
----------- -----------
12 11
(1 rows affected)