Altering a Table: A Basic Form : ALTER TABLE « Table « SQL Server / T-SQL Tutorial






  1. SQL Server / T-SQL Tutorial
  2. Table
  3. ALTER TABLE
ALTER TABLE table_name
        ADD col_name type [NULL | IDENTITY]
        [{, col_name type [NULL | IDENTITY]} ...]
        DROP COLUMN col_name [{, col_name ...]
        ALTER COLUMN col_name type {NULL | IDENTITY}
        [{, col_name type NULL | IDENTITY} ...]


12> CREATE TABLE employee(
13>    id          INTEGER NOT NULL PRIMARY KEY,
14>    first_name  VARCHAR(10),
15>    last_name   VARCHAR(10),
16>    salary      DECIMAL(10,2),
17>    start_Date  DATETIME,
18>    region      VARCHAR(10),
19>    city        VARCHAR(20),
20>    managerid   INTEGER
21> );
22> 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> ALTER TABLE employee
4>         ADD telephone_no CHAR(12) NULL
5>
6>
7> select * from employee;
8> GO
id          first_name last_name  salary       start_Date              region     city                 managerid   telephone_no
----------- ---------- ---------- ------------ ----------------------- ---------- -------------------- ----------- ------------
          1 Jason      Martin          5890.00 2005-03-22 00:00:00.000 North      Vancouver                      3 NULL
          2 Alison     Mathews         4789.00 2003-07-21 00:00:00.000 South      Utown                          4 NULL
          3 James      Smith           6678.00 2001-12-01 00:00:00.000 North      Paris                          5 NULL
          4 Celia      Rice            5567.00 2006-03-03 00:00:00.000 South      London                         6 NULL
          5 Robert     Black           4467.00 2004-07-02 00:00:00.000 East       Newton                         7 NULL
          6 Linda      Green           6456.00 2002-05-19 00:00:00.000 East       Calgary                        8 NULL
          7 David      Larry           5345.00 2008-03-18 00:00:00.000 West       New York                       9 NULL
          8 James      Cat             4234.00 2007-07-17 00:00:00.000 West       Regina                         9 NULL
          9 Joan       Act             6123.00 2001-04-16 00:00:00.000 North      Toronto                       10 NULL

(9 rows affected)
1> drop table employee;
2> GO
1>
2>








3.2.ALTER TABLE
3.2.1.The basic syntax of the ALTER TABLE statement
3.2.2.drop column syntax
3.2.3.Change the length of the emp_name column in the employee table from varchar(30) to varchar(50)
3.2.4.Alter table to add a constraint based on IN function
3.2.5.Altering a Table: A Basic Form
3.2.6.Alter table to add column
3.2.7.Alter table to drop a column
3.2.8.The DROP COLUMN clause provides the ability to drop an existing column of the table.
3.2.9.ALTER data size for a COLUMN
3.2.10.Altering a Table: Enhanced Form
3.2.11.Use ALTER TABLE statement to define the primary key
3.2.12.Use ALTER TABLE statement to define the foreign key of a table.
3.2.13.Each declarative integrity constraint can be removed using the DROP clause of the ALTER TABLE statement.
3.2.14.Expanded nvarchar(20) to nvarchar(300)
3.2.15.Creating a Computed Column in alter table command
3.2.16.Create a Table Index