MySQL dynamic Add a deletion column field command

How does MySQL dynamically add a pruning column field, as sql:

Dynamically add column fields:

ALERT TABLE table1 Add transactor varchar (a) not Null;

To delete a column field dynamically:

ALERT TABLE tablename drop column field_id;

To modify a column field dynamically:

ALERT TABLE table_name Change old_field_name new_field_name field_type;

Dynamically modifying table Structures

ALERT TABLE table_name MODIFY field_name Field_type

Add after creating table: ALTER TABLE tablename add ID int auto_increment PRIMARY key

Set the self-add field initial value: ALTER TABLE tablename auto_increment =x;

Set PRIMARY key: ALTER TABLE TableName add primary key (Field_name);

Creating a composite primary key: CREATE TABLE tablename (
                                    Studentno int,
                                    CourseID int,
                                    score int,
                                    primary KEY (Studentno,courseid);

Set composite PRIMARY key: ALTER TABLE TableName add PRIMARY key (column 1, column 2, column 3);

Renaming table: ALTER TABLE table_old_name rename Table_new_name;

Change the type of field: ALTER TABLE tablename modify Field_name Field_type;

Rename field: ALTER TABLE tablename change Old_field_name new_field_name new_field_type;

Delete field: ALTER TABLE tablename drop column field_name;

Add a new field: ALTER TABLE tablename add New_field_name field_type;

New field with default value of 0, Non-empty: ALTER TABLE tablename add New_field_name field_type NOT null default ' 0 ';

New field with default value of 0, Non-null, Tabelname, PRIMARY key: ALTER TABLE add New_field_name field_type default 0 NOT NULL auto_increment, add primary Key (New_field_name);

To modify a field type:

ALTER TABLE tablename change Filed_name filed_name new_type;