в 13:46, 26 мая 2010

2010-05-26T13:46:06Z

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2010-05-26T10:21:22Z

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==Combine two columns as the primary key==



<source lang="sql">

1>
2> CREATE TABLE ClassGrades(
3> ClassID int,
4> StudentID int,
5> GradeLetter varchar(2),
6> Constraint PK_ClassGrades PRIMARY KEY(ClassID, StudentID)
7> )
8> GO
1>
2> INSERT ClassGrades VALUES(1,1,"A")
3> GO
(1 rows affected)
1> INSERT ClassGrades VALUES(1,2,"B-")
2> GO
(1 rows affected)
1> INSERT ClassGrades (ClassID, GradeLetter) VALUES(1,"C-")
2> GO
Msg 515, Level 16, State 2, Server sqle\SQLEXPRESS, Line 1
Cannot insert the value NULL into column "StudentID", table "master.dbo.ClassGrades"; column does not allow nulls. INSERT fails.
The statement has been terminated.
1> select * from ClassGrades
2> GO
ClassID StudentID GradeLetter
----------- ----------- -----------
1 1 A
1 2 B-
(2 rows affected)
1>
2> drop ClassGrades
3> GO
Msg 102, Level 15, State 1, Server sqle\SQLEXPRESS, Line 2
Incorrect syntax near "ClassGrades".
1>
2>

</source>

==Define Primary key in table creation command==



<source lang="sql">

20>
21> CREATE TABLE employee (emp_no INTEGER NOT NULL,
22> emp_fname CHAR(20) NOT NULL,
23> emp_lname CHAR(20) NOT NULL,
24> dept_no CHAR(4) NULL,
25> CONSTRAINT prim_empl PRIMARY KEY (emp_no))
26> GO
1>
2> drop table employee
3> GO
1>
2> --
3>

</source>

==Specification of the primary key of the employee table as a column-level constraint==



<source lang="sql">
1> -- Specification of the primary key of the employee table as a column-level constraint.
2> CREATE TABLE employee
3> (emp_no INTEGER NOT NULL CONSTRAINT prim_empl PRIMARY KEY,
4> emp_fname CHAR(20) NOT NULL,
5> emp_lname CHAR(20) NOT NULL,
6> dept_no CHAR(4) NULL)
7> GO
1> drop table employee
2> GO
1>

</source>

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SQL Server/T-SQL/Constraints/Primary key - История изменений

в 13:46, 26 мая 2010

Admin: 1 версия