Check out example codes for "change data type in mysql". It will help you in understanding the concepts better.

Code Example 1

ALTER TABLE table_name

MODIFY column_name datatype;

Code Example 2

ALTER TABLE table_name

CHANGE COLUMN column_name column_name datatype;

Code Example 3

ALTER TABLE table_name

ADD column_name datatype;

Code Example 4

ALTER TABLE table
ADD COLUMN column VARCHAR (255) NOT NULL AFTER column;

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