SQL Server/T-SQL/Transact SQL/Declare Variables
Содержание
Declare a varchar variable
<source lang="sql">
1> -- DATALENGTH(): returns the number of bytes used to manage a value. 2> 3> DECLARE @Value VarChar(20) 4> SET @Value = "abc" 5> 6> SELECT DATALENGTH(@Value) 7> GO
3
(1 rows affected) 1>
</source>
Declare a variable
<source lang="sql">
1> create table employee( 2> ID int, 3> name nvarchar (10), 4> salary int, 5> start_date datetime, 6> city nvarchar (10), 7> region char (1)) 8> GO 1> 2> insert into employee (ID, name, salary, start_date, city, region) 3> values (1, "Jason", 40420, "02/01/94", "New York", "W") 4> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (2, "Robert",14420, "01/02/95", "Vancouver","N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (3, "Celia", 24020, "12/03/96", "Toronto", "W") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (4, "Linda", 40620, "11/04/97", "New York", "N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (5, "David", 80026, "10/05/98", "Vancouver","W") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (6, "James", 70060, "09/06/99", "Toronto", "N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (7, "Alison",90620, "08/07/00", "New York", "W") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (8, "Chris", 26020, "07/08/01", "Vancouver","N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (9, "Mary", 60020, "06/09/02", "Toronto", "W") 3> GO (1 rows affected) 1> 2> select * from employee 3> GO ID name salary start_date city region
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1 Jason 40420 1994-02-01 00:00:00.000 New York W 2 Robert 14420 1995-01-02 00:00:00.000 Vancouver N 3 Celia 24020 1996-12-03 00:00:00.000 Toronto W 4 Linda 40620 1997-11-04 00:00:00.000 New York N 5 David 80026 1998-10-05 00:00:00.000 Vancouver W 6 James 70060 1999-09-06 00:00:00.000 Toronto N 7 Alison 90620 2000-08-07 00:00:00.000 New York W 8 Chris 26020 2001-07-08 00:00:00.000 Vancouver N 9 Mary 60020 2002-06-09 00:00:00.000 Toronto W
(9 rows affected) 1> 2> DECLARE @ValueToUpdate VARCHAR(10) 3> 4> SET @ValueToUpdate = "Mick Bagram" 5> 6> UPDATE Employee 7> SET Name = @ValueToUpdate 8> GO (9 rows affected) 1> 2> select * from employee 3> GO ID name salary start_date city region
---------- ----------- ----------------------- ---------- ------
1 Mick Bagra 40420 1994-02-01 00:00:00.000 New York W 2 Mick Bagra 14420 1995-01-02 00:00:00.000 Vancouver N 3 Mick Bagra 24020 1996-12-03 00:00:00.000 Toronto W 4 Mick Bagra 40620 1997-11-04 00:00:00.000 New York N 5 Mick Bagra 80026 1998-10-05 00:00:00.000 Vancouver W 6 Mick Bagra 70060 1999-09-06 00:00:00.000 Toronto N 7 Mick Bagra 90620 2000-08-07 00:00:00.000 New York W 8 Mick Bagra 26020 2001-07-08 00:00:00.000 Vancouver N 9 Mick Bagra 60020 2002-06-09 00:00:00.000 Toronto W
(9 rows affected) 1> 2> 3> 4> drop table employee 5> GO 1>
</source>
Declares a local variable (@intvar) and then assigns a value to the variable
<source lang="sql">
1> create table employee( 2> ID int, 3> name nvarchar (10), 4> salary int, 5> start_date datetime, 6> city nvarchar (10), 7> region char (1)) 8> GO 1> 2> insert into employee (ID, name, salary, start_date, city, region) 3> values (1, "Jason", 40420, "02/01/94", "New York", "W") 4> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (2, "Robert",14420, "01/02/95", "Vancouver","N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (3, "Celia", 24020, "12/03/96", "Toronto", "W") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (4, "Linda", 40620, "11/04/97", "New York", "N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (5, "David", 80026, "10/05/98", "Vancouver","W") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (6, "James", 70060, "09/06/99", "Toronto", "N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (7, "Alison",90620, "08/07/00", "New York", "W") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (8, "Chris", 26020, "07/08/01", "Vancouver","N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (9, "Mary", 60020, "06/09/02", "Toronto", "W") 3> GO (1 rows affected) 1> 2> select * from employee 3> GO ID name salary start_date city region
---------- ----------- ----------------------- ---------- ------
1 Jason 40420 1994-02-01 00:00:00.000 New York W 2 Robert 14420 1995-01-02 00:00:00.000 Vancouver N 3 Celia 24020 1996-12-03 00:00:00.000 Toronto W 4 Linda 40620 1997-11-04 00:00:00.000 New York N 5 David 80026 1998-10-05 00:00:00.000 Vancouver W 6 James 70060 1999-09-06 00:00:00.000 Toronto N 7 Alison 90620 2000-08-07 00:00:00.000 New York W 8 Chris 26020 2001-07-08 00:00:00.000 Vancouver N 9 Mary 60020 2002-06-09 00:00:00.000 Toronto W
(9 rows affected) 1> 2> --Declares a local variable (@intvar) and then assigns a value to the variable. 3> 4> DECLARE @intvar int 5> SET @intvar = 1 6> 7> SELECT ID, Name "Employee name", 8> @intvar "Local variable" 9> FROM Employee 10> GO ID Employee name Local variable
------------- --------------
1 Jason 1 2 Robert 1 3 Celia 1 4 Linda 1 5 David 1 6 James 1 7 Alison 1 8 Chris 1 9 Mary 1
(9 rows affected) 1> 2> drop table employee 3> GO 1>
</source>
Table Variables
<source lang="sql">
4> 5> 6> DECLARE @T1 TABLE(col1 INT); 7> INSERT @T1 VALUES(1); 8> SELECT * FROM @T1; 9> GO col1
1
1> 2>
</source>
Use declared variable in SQL statement
<source lang="sql">
1> create table employee( 2> ID int, 3> name nvarchar (10), 4> salary int, 5> start_date datetime, 6> city nvarchar (10), 7> region char (1)) 8> GO 1> 2> insert into employee (ID, name, salary, start_date, city, region) 3> values (1, "Jason", 40420, "02/01/94", "New York", "W") 4> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (2, "Robert",14420, "01/02/95", "Vancouver","N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (3, "Celia", 24020, "12/03/96", "Toronto", "W") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (4, "Linda", 40620, "11/04/97", "New York", "N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (5, "David", 80026, "10/05/98", "Vancouver","W") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (6, "James", 70060, "09/06/99", "Toronto", "N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (7, "Alison",90620, "08/07/00", "New York", "W") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (8, "Chris", 26020, "07/08/01", "Vancouver","N") 3> GO (1 rows affected) 1> insert into employee (ID, name, salary, start_date, city, region) 2> values (9, "Mary", 60020, "06/09/02", "Toronto", "W") 3> GO (1 rows affected) 1> 2> select * from employee 3> GO ID name salary start_date city region
---------- ----------- ----------------------- ---------- ------
1 Jason 40420 1994-02-01 00:00:00.000 New York W 2 Robert 14420 1995-01-02 00:00:00.000 Vancouver N 3 Celia 24020 1996-12-03 00:00:00.000 Toronto W 4 Linda 40620 1997-11-04 00:00:00.000 New York N 5 David 80026 1998-10-05 00:00:00.000 Vancouver W 6 James 70060 1999-09-06 00:00:00.000 Toronto N 7 Alison 90620 2000-08-07 00:00:00.000 New York W 8 Chris 26020 2001-07-08 00:00:00.000 Vancouver N 9 Mary 60020 2002-06-09 00:00:00.000 Toronto W
(9 rows affected) 1> 2> BEGIN TRAN Restore_Value 3> 4> DECLARE @ValueToUpdate VARCHAR(30) 5> 6> SET @ValueToUpdate = "S B" 7> 8> UPDATE Employee 9> SET Name = @ValueToUpdate 10> WHERE ID = 5 11> 12> ROLLBACK TRAN Restore_Value 13> GO (1 rows affected) 1> 2> SELECT * FROM Employee 3> GO ID name salary start_date city region
---------- ----------- ----------------------- ---------- ------
1 Jason 40420 1994-02-01 00:00:00.000 New York W 2 Robert 14420 1995-01-02 00:00:00.000 Vancouver N 3 Celia 24020 1996-12-03 00:00:00.000 Toronto W 4 Linda 40620 1997-11-04 00:00:00.000 New York N 5 David 80026 1998-10-05 00:00:00.000 Vancouver W 6 James 70060 1999-09-06 00:00:00.000 Toronto N 7 Alison 90620 2000-08-07 00:00:00.000 New York W 8 Chris 26020 2001-07-08 00:00:00.000 Vancouver N 9 Mary 60020 2002-06-09 00:00:00.000 Toronto W
(9 rows affected) 1> 2> drop table employee 3> GO 1>
</source>