Alter table command is used for altering tables, table fields and table indexes

To rename a table:

ALTER TABLE mytable RENAME yourtable;

To add a column:

ALTER TABLE mytable ADD COLUMN update TIMESTAMP FIRST
ALTER TABLE mytable ADD COLUMN update TIMESTAMP AFTER id
ALTER TABLE mytable ADD COLUMN update TIMESTAMP LAST

The first example create a column in the first position. The second command creates a column after the column id. The last example creates a column in the last position.

To drop a column:

ALTER TABLE mytable DROP COLUMN update

To drop an index:

ALTER TABLE mytable DROP INDEX myindex

To modify a column:

ALTER TABLE mytable CHANGE sid sidi INT(10) NOT NULL

We simply specified that the column we wish to modify is sid and then specified its properties.