SQL ALTER TABLE Statement
Change Data Type :
Now we want to change the data type of the column named "DateofBirth" in the "Customers" table.we use the following SQL statement:
ALTER TABLE Customers ALTER COLUMN DateOfBirth year
The ALTER TABLE statement is used Modify the structure of a Table. In general we can use Alter Table statement to add, delete, or modify
columns in an existing table.
Syntax:
To add a column in a table, use the following syntax:
ALTER TABLE table_name ADD column_name datatype
To delete a column in a table, use the following syntax
(notice that some database systems don't allow deleting a column):
ALTER TABLE table_name DROP COLUMN column_name
To change the data type of a column in a table, use the
following syntax:
SQL Server / MS Access:
ALTER TABLE table_name ALTER COLUMN column_name datatype
My SQL / Oracle:
ALTER TABLE table_name MODIFY column_name datatype
To add a column named "DateOfBirth" in
the "Customers" table :
ALTER TABLE Customers ADD DateOfBirth date
Notice that the new column, "DateOfBirth", is of
type date and is going to hold a date. The data type specifies what type of
data the column can hold.
Now we want to change the data type of the column named "DateofBirth" in the "Customers" table.we use the following SQL statement:
Notice that the "DateOfBirth" column is now of
type year and is going to hold a year in a two-digit or four-digit format.
DROP COLUMN :
Next, we want to delete the column named
"DateOfBirth" in the "Customers" table.
We use the following SQL statement:
ALTER TABLE Customers DROP COLUMN DateOfBirth
Thanks, TAMATAM
Thanks, TAMATAM
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