摘要：
1.使用create or replace view命令创建视图语法格式：create or replace view 视图名as select 查询子句例子：create or replace view tb_user_view1 as select count(username) shuliang,username from tb_user group by username order by shuliang asc2.使用create or replace view命令修改视图语法格式：create or replace view 视图名as select 查询子句例子：create 阅读全文