首发公众号：码农架构
视图就是虚拟表:
如何创建，更新和删除视图
创建视图：CREATE VIEW
CREATE VIEW player_above_avg_height AS
SELECT player_id, height
FROM player
WHERE height > (SELECT AVG(height) from player)当视图创建之后，它就相当于一个虚拟表，可以直接使用：
SELECT * FROM player_above_avg_height嵌套视图
CREATE VIEW player_above_above_avg_height AS
SELECT player_id, height
FROM player
WHERE height > (SELECT AVG(height) from player_above_avg_height)修改视图：ALTER VIEW
ALTER VIEW view_name AS
SELECT column1, column2
FROM table
WHERE condition删除视图：DROP VIEW
DROP VIEW view_name需要说明的是，SQLite 不支持视图的修改，仅支持只读视图，也就是说你只能使用 CREATE VIEW 和 DROP VIEW，如果想要修改视图，就需要先 DROP 然后再 CREATE。
如何使用视图简化 SQL 操作
利用视图完成复杂的连接
CREATE VIEW player_height_grades AS
SELECT p.player_name, p.height, h.height_level
FROM player as p JOIN height_grades as h
ON height BETWEEN h.height_lowest AND h.height_highest利用视图对数据进行格式化
CREATE VIEW player_team AS
SELECT CONCAT(player_name, '(' , team.team_name , ')') AS player_team FROM player JOIN team WHERE player.team_id = team.team_id使用视图与计算字段
CREATE VIEW game_player_score AS
SELECT game_id, player_id, (shoot_hits-shoot_3_hits)*2 AS shoot_2_points, shoot_3_hits*3 AS shoot_3_points, shoot_p_hits AS shoot_p_points, score FROM player_score总结
使用视图有很多好处，比如安全、简单清晰。
