Add a new column to the existing table:
alter table table_name add(column_name type(size)) 或者 alter table table_name add column_name type(size)
Delete a column in an existing table:
alter table table_name drop column column_name
Modify the field name of a column in the table:
alter table table_name rename column column_name_old to column_name_new
Modify the type of a column field in the table:
alter table table_name modify column_name type(size)
