sql - MySQL 表视图限制

Question

SQL Views for MySQL的功能是否有任何限制？

例如：您可以使用“JOIN”命令创建表视图吗？

Answer 1

You should read Restrictions on Views for details on view limitations.

Answer 2

MySQL allows JOIN commands

MySQL Create View syntax

Answer 3

Regarding JOIN, yes:

mysql> create table foo (i int);
Query OK, 0 rows affected (0.03 sec)

mysql> create table bar (i int);
Query OK, 0 rows affected (0.03 sec)

mysql> create view foobar as select foo.i as foo_i, bar.i as bar_i from foo join bar on (foo.i=bar.i);
Query OK, 0 rows affected (0.02 sec)

But as others answers pointed, the manual is a great resource.

Answer 4

Short answer - yes. In two words view just named select (without order by of course).

Answer 5

与 SQL 中的所有其他内容一样，语法、功能和可能性取决于您正在使用的数据库管理系统。但是加入表格是非常基本的东西。没有它，视图就没有多大用处。

Answer 6

1. 临时表：

   CREATE TEMPORARY TABLE super (id int);
   
   mysql> CREATE OR REPLACE view cat AS SELECT * FROm super;
   
   ERROR 1352 (HY000): View's SELECT refers to a temporary table 'super'
   

2. 系统和本地变量：

   mysql> SELECT @sosize;//1000
   
   mysql> CREATE OR REPLACE view cat AS SELECT *,@sosize FROm super;
   ERROR 1351 (HY000): View's SELECT contains a variable or parameter
   

3. 子查询：

   CREATE OR REPLACE view cat AS SELECT * FROm SELECT * FROM super;
   ERROR 1349 (HY000): View's SELECT contains a subquery in the FROM clause