一 视图html
预先定义一种对应关系,如:temp_table <-----> select * from class where student_id >10,那么这种对应关系叫作视图。python
它仅仅是一种对应关系,当之后调用时,是会从新从内存中拿右侧的真正的表。视图是临时的,没有真是存在内存中的。 mysql
建立视图:sql
create view temp_table as select * from class where student_id >10
删除视图:ide
drop view temp_table
修改视图:函数
alter view temp_table as .......
使用视图:oop
select * from temp_table
二 存储过程fetch
先预先定义一个语句,如 tmp_table <==> select * from class where student_id >10, 当咱们调用这个语句的时候会返回给咱们结果,至关于函数。spa
建立存储过程:3d
delimiter .. #delimiter 用来修改执行语句的结尾符,默认是';' ,这里修改成'..'
create procedure tmp_table()
begin
select * from class;
end ..
调用存储过程:
call tmp_table()
存储过程不推荐修改,就直接删掉而后重建。
pymysql中使用存储过程:
import pymysql connection = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='', db='test', charset="utf8") cursor = connection.cursor(cursor=pymysql.cursors.DictCursor) cursor.callproc('tmp_table') result = cursor.fetchall() cursor.close() connection.close()
存储过程能够接受参数,参数有三种:
a. in 用于传入参数
b. out 用于返回值用
c. inout 便可以传入又能够当返回值 建立带有参数的存储过程:
delimiter //
create procedure tmp_table( in arg1 int, out arg2 int, inout arg3 int ) begin declare temp1 int;
declare temp2 int default 1;
set temp1 = 2;
set arg2 = temp1 + temp2;
set arg3 = arg2 + 10; end//
delimiter ;
declare @arg2 int default 1; 声明变量, 默认值为1
declare @arg3 int default 1; 声明变量, 默认值为1
set @arg2 = 4; 给变量赋值
set @arg3 = 5
call tmp_table(1, @arg2, @arg3)
select @arg2,@arg3;
pymysql执行带有参数的存储过程:
import pymysql connection = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='', db='test', charset="utf8") cursor = connection.cursor(cursor=pymysql.cursors.DictCursor) cursor.callproc('tmp_table', args=(1,22,33)) cursor.execute("select @_tmp_table_0,@_tmp_table_1,@_tmp_table_2") #取出返回参数的固定用法 print(cursor.fetchall()) connection.commit() cursor.close() connection.close()
例子:建立存储过程:
pymysql执行代码就是上面的,结果:
若是在存储过程当中有相似select * from '表名', 那么只需在python代码中,cursor.callproc()下面紧跟着执行 cursor.fetchall()就能拿到结果。
条件语句
delimiter \\ CREATE PROCEDURE proc_if () BEGIN declare i int default 0; if i = 1 THEN SELECT 1; ELSEIF i = 2 THEN SELECT 2; ELSE SELECT 7; END IF; END\\ delimiter ;
循环语句
delimiter \\ CREATE PROCEDURE proc_while () BEGIN DECLARE num INT ; SET num = 0 ; WHILE num < 10 DO SELECT num ; SET num = num + 1 ; END WHILE ; END\\ delimiter ;
delimiter \\ CREATE PROCEDURE proc_repeat () BEGIN DECLARE i INT ; SET i = 0 ; repeat select i; set i = i + 1; until i >= 5 end repeat; END\\ delimiter ;
BEGIN declare i int default 0; loop_label: loop set i=i+1; if i<8 then iterate loop_label; end if; if i>=10 then leave loop_label; end if; select i; end loop loop_label; END
动态执行SQL语句
delimiter \\ DROP PROCEDURE IF EXISTS proc_sql \\ CREATE PROCEDURE proc_sql () BEGIN declare p1 int; set p1 = 11; set @p1 = p1; PREPARE prod FROM 'select * from tb2 where nid > ?'; EXECUTE prod USING @p1; DEALLOCATE prepare prod; END\\ delimiter ; 动态执行SQL
以上语句参考了本片文章:https://www.cnblogs.com/wupeiqi/articles/5713323.html 十分感谢!