1、MySQL创建索引
创建普通索引:
CREATE INDEX index_name ON table_name (column_name);
示例:
CREATE INDEX idx_phone on t_user(phone);
组合索引:
CREATE INDEX idx_person_name on t_user(first_name,last_name);
创建唯一索引:
CREATE UNIQUE INDEX index_name ON table_name (column_name);
示例:CREATE UNIQUE INDEX idx_username ON t_user(username);
2、MySQL修改字段及注释
修改字段长度:
ALTER TABLE table_name MODIFY COLUMN column_name column_type(length);
示例:
ALTER TABLE t_user MODIFY COLUMN user_name varchar(32) default "" COMMENT '用户名';