ALTER TABLE

The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.

To change the data type of a multiple column in a table, use the following syntax

ALTER TABLE table_name
 (
   Column_1_name datatype ,
   Column_2_name datatype ,
   Column_3_name datatype ,
   Column_4_name datatype ,
   Column_5_name datatype ,
   Column_6_name datatype ,
   Column_7_name datatype ,
)

To change the data type of a single column in a table, use the following syntax

ALTER TABLE table_name
 (
    ALTER COLUMN Column_3_name datatype
)

To add a column in a table, use the following syntax

ALTER TABLE table_name
 (
    ADD Column_8_name datatype
)

To delete a column in a table, use the following syntax

ALTER TABLE table_name
 (
    DROP COLUMN Column_4_name
)