CREATE TABLE

DROP TABLE IF EXISTS words;
CREATE TABLE words (
  id bigint(20) NOT NULL AUTO_INCREMENT,
  word varchar(100) DEFAULT NULL,
  PRIMARY KEY (id)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

ALTER TABLE

新增字段

ALTER TABLE words ADD COLUMN cc_word int unsigned not null default 0 AFTER word;

新增索引

ALTER TABLE words2 ADD INDEX idx_word ( word )
ALTER TABLE words ADD INDEX idx_word ( cc_word )

官方资料

官方文档-sql-data-definition-statements