Check out example codes for "alter column sql". It will help you in understanding the concepts better.

Code Example 1

ALTER TABLE table_name
ALTER COLUMN column_name datatype;
--ex.
ALTER TABLE Customers
ADD Email varchar(255);

Code Example 2

ALTER TABLE table_name
ALTER COLUMN column_name datatype;

-- Example
ALTER TABLE product
ALTER COLUMN description VARCHAR(250);

Code Example 3

ALTER TABLE table_name 
ADD column_name datatype;

Code Example 4

ALTER TABLE table_name 
ALTER COLUMN column_name new_data_type(size);

Code Example 5

ALTER TABLE table_name

MODIFY column_name datatype;

Code Example 6

ALTER TABLE table_name
ALTER COLUMN column_name datatype;

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