MySQL ALTER TABLE: ALTER vs CHANGE vs MODIFY COLUMN

ALTER COLUMN

Used to set or remove the default value for a column. Example:

ALTER TABLE MyTable ALTER COLUMN foo SET DEFAULT 'bar';
ALTER TABLE MyTable ALTER COLUMN foo DROP DEFAULT;

CHANGE COLUMN

Used to rename a column, change its datatype, or move it within the schema. Example:

ALTER TABLE MyTable CHANGE COLUMN foo bar VARCHAR(32) NOT NULL FIRST;
ALTER TABLE MyTable CHANGE COLUMN foo bar VARCHAR(32) NOT NULL AFTER baz;

MODIFY COLUMN

Used to do everything CHANGE COLUMN can, but without renaming the column. Example:

ALTER TABLE MyTable MODIFY COLUMN foo VARCHAR(32) NOT NULL AFTER baz;

The official documentation for ALTER TABLE (for MySQL 5.1) is here.

出处：https://hoelz.ro/ref/mysql-alter-table-alter-change-modify-column