SQL Server/T-SQL/Constraints/Unique

Материал из SQL эксперт
Перейти к: навигация, поиск

Adding a UNIQUE Constraint to an Existing Table

   <source lang="sql">

125> 126> CREATE TABLE employee( 127> id INTEGER NOT NULL PRIMARY KEY, 128> first_name VARCHAR(10), 129> last_name VARCHAR(10), 130> salary DECIMAL(10,2), 131> start_Date DATETIME, 132> region VARCHAR(10), 133> city VARCHAR(20), 134> managerid INTEGER 135> ); 136> 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 2" , "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 2    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> ALTER TABLE employee 4> ADD CONSTRAINT UNQ_Name 5> UNIQUE (first_Name) 6> GO 1> 2> 3> 4> 5> drop table employee; 6> GO 1> 

</source>


Add Unique constaint to table creation

   <source lang="sql">

17> 18> -- Add Unique constaint to table creation 19> CREATE TABLE projects (project_no CHAR(4) DEFAULT "p1", 20> project_name CHAR(15) NOT NULL, 21> budget FLOAT NULL 22> CONSTRAINT unique_no UNIQUE (project_no)) 23> GO 1> 2> drop table projects 3> GO 1> 

      </source>


A unique constraint

   <source lang="sql">

5> CREATE TABLE MyTable ( 6> MyID Int IDENTITY(1,1) NOT NULL , ID Int NOT NULL 7> , Description nVarChar(50) 8> , Region nVarChar(10) DEFAULT "PNW" 9> , CONSTRAINT MyTable_PK PRIMARY KEY NONCLUSTERED (MyID,ID)) 10> GO 1> 2> drop table MyTable; 3> GO 

</source>
Источник — «http://sqle.ru/index.php?title=SQL_Server/T-SQL/Constraints/Unique&oldid=6125»