SQL Server/T-SQL/Transact SQL/Declare Variables

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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>

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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


---------- ----------- ----------------------- ---------- ------
         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>

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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>

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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>

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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>

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