MYSQL视图 事务 游标 索引及其使用

select * from(select nid,name from tb1 where nid > 2) As A where A.NAME > 'alex';
#创建视图
create view vi As
select nid,name from A WHERE nid > a;
#删除视图
drop view vi

#修改视图
alter view vi As
select A.nid,B.NAME FROM A
left join B ON A.id = B.nid
left join C ON A.id = C.nid
WHERE
A.id > 2
AND C.nid < 5
#使用视图
select * from vi

#事务

delimiter //
create procedure p1(
OUT p_return_code tinyint
)
BEGIN
DECLEAR exit handler for sqlexception
BEGIN
--ERROR
set p_return_code = 1;
rollback;
END;

DECLEAR exit handler for sqlwarning
BEGIN
--WARNING
set p_return_code = 2;
rollback;
END;

START TRANSACTION;
DELETE from tb1;
insert into tb(name) values ('seven');
COMMIT;

--SUCCESS
set p_return_code = 0;

END\
delimiter ;

#游标
delimiter //
create procedure p3()
begin
declare ssid int; --自定义变量1
declare ssname varchar(50); --自定义变量2
DECLARE done INT DEFAULT FALSE;

DECLARE my_cursor CURSOR FOR select sid,sname from student;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = True;

open my_cursor;
xxoo: LOOP
fetch my_cursor into ssid,ssname;
if done then
leave xxoo;
END IF;
insert into teacher(tname) values(ssname);
end loop xxoo;
close my_cursor;
end //
delimiter ;

#动态执行SQL
delimiter \
CREATE PROCEDURE p4(
in nid int
)
BEGIN
PREPARE prod FROM 'select * from student where nid > ?';
EXECUTE prod USING @nid;
DEALLOCATE prepare prod;
END\
delimiter ;

#删除存储过程
drop procedure proc_name;
#执行存储过程
--无参数
call proc_name()

--有参数
call proc_name(1,2)

--有参数，有in, out, inout
set @t1=0;
set @t2=3;
call proc_name(1,2,@t1,@t2)

#自定义函数

delimiter \
create function f1(
i1 int,
i2 int)
return int
BEGIN
declare num int;
set num = i1 + i2;
return(num);
END \
delimiter ;

#删除函数
drop function func_name;

#执行函数
#1.获取返回值
declare @i VARCHAR(32);
select UPPER('alex') into @i;
SELECT @i;
#2.在查询中使用
select f1(li,nid), name from tb2;

#支持事务的存储过程

set @i = 0;
call p1(@i);
select @i;

class UserInfoRespository:
def get_all(self):
sql = 'select * from uesrinfo'
return fetchall()
def get_one_by_user_pwd(self, username, password):
sql = 'select * from userinfo where username=%s and password=%s'
cursor.execute(sql,username,password)
return cursor.fetchone()
def add():
sql = "insert into userinfo(...) values (...)"
conn.commit()
obj = UserInfoRespository()
obj.get()

#索引
#创建表+索引
普通索引：加速查询
create table in1(
nid int not null auto_increment primary key,
name varchar(32) not null,
email varchar(64) not null,
extra text,
index ix_name (name)
)

#创建索引
create index index_name on table_name(column_name);
#删除索引
drop index_name on table_name;
#查看索引
show index from table_name;
#如果创建索引时BLOB和TEXT类型，必须指定length
create index ix_extra on ini(extra(32))

2.唯一索引
加速查询和唯一约束（可含null）
创建表+唯一索引
create table in1(
nid int not null auto_increment primary key,
name varchar(32) not null,
email varchar(64) not null,
extra text,
unique ix_name (name)
)

#创建唯一索引
create unique index 索引名 on 表名(列名);

#删除唯一索引
drop unique index 索引名 on 表名;

3.主键索引
加速查询和唯一约束（不可含null）
create table in1(
nid int not null auto_increment primary key,
name varchar(32) not null,
email varchar(64) not null,
extra text,
index ix_name (name)
)

OR

create table in1(
nid int not null auto_increment,
name varchar(32) not null,
email varchar(64) not null,
extra text,
primary key(nid),
index ix_name (name)
)

#创建主键
alter table 表名 add primary key(列名)；
#删除主键
alter table 表名 drop primary key;
alter table 表名 modify 列名 int, drop primary key;

#组合索引
创建组合索引
create index ix_name_email on in3(name, email);

repeat循环
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 ;

loop循环
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 EXIST 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;