CREATE TABLE t_message(
id INT UNSIGNED PRIMARY KEY,
content VARCHAR(200) NOT NULL,
type ENUM("公告","通报","个人通知") NOT NULL,
create_time TIMESTAMP NOT NULL,
INDEX idx_type (type)
);
DROP INDEX idx_type ON t_message;
CREATE INDEX idx_type ON t_message(type);
SHOW INDEX FROM t_message;
ALTER TABLE t_message ADD INDEX idx_type(type);