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SQL ALTER TABLE Statement

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admin
Tuesday, April 12, 2011 - 20:02


The ALTER TABLE statement is used to change the structure of an existing table like adding, deleting, or modifying of column.

SQL ALTER TABLE Syntax

To add a new column to the existing table use the following syntax:

  1.  ALTER TABLE table_name
  2.     ADD column_name datatype

To remove a column from a table use the following syntax:

  1.  ALTER TABLE table_name
  2.     DROP TABLE column_name

To modify a column from a table use the following syntax:

  1.  ALTER TABLE table_name
  2.     ALTER COLUMN column_name datatype

Consider the following table for this exercise

Users

Firstname Lastname Salary DeptID
John Smith 1000 1
Mathew Simon 3000 1
Bill Steve 2200 1
Amanda Rogers 1800 2
Steve Hills 2800 2
Steve jobs 2400 2
bill cosby 700 3

Example # 1

ALTER TABLE Users ADD Phone INT

Result of the Query

Firstname Lastname Salary DeptID Phone
John Smith 1000 1  
Mathew Simon 3000 1  
Bill Steve 2200 1  
Amanda Rogers 1800 2  
Steve Hills 2800 2  
Steve jobs 2400 2  
bill cosby 700 3  

The resulted table is now formed with an additional column of Phone that we created with the alter table statement.



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sql tutorial
ALTER TABLE Statement
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