事物与存储过程

#建库、建表、添加数据
CREATE DATABASE chapter06;
USE chapter06;
CREATE TABLE account(
id INT primary key auto_increment,
name VARCHAR(40),
money FLOAT
);
INSERT INTO account(name,money) VALUES('a',1000);
INSERT INTO account (name, money) VALUES ('b', 1000);

【例6-1】
START TRANSACTION;
UPDATE account SET money=money-100 WHERE NAME='a';
UPDATE account SET money=money+100 WHERE NAME='b';
COMMIT;

#查询
SELECT * FROM account;
-----------------------------------------------------------------------------------------------
6.1.2 事务的提交

#使用UPDATE语句实现由b账户向a账户转100元钱的转账功能，
START TRANSACTION;
UPDATE account SET money=money+100 WHERE name='a';
UPDATE account SET money=money-100 WHERE name='b';

#查询
SELECT * FROM account;

#使用commit语句来提交事务
START TRANSACTION;
UPDATE account SET money=money+100 WHERE name='a';
UPDATE account SET money=money-100 WHERE name='b';
COMMIT;

------------------------------------------------------------------------------------------------

6.1.3 事务的回滚

#使用UPDATE语句实现由b账户向a账户转100元钱的转账功能，
START TRANSACTION;
UPDATE account SET money=money+100 WHERE name='a';
UPDATE account SET money=money-100 WHERE name='b';

#事务回滚
ROLLBACK;

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6.1.4 事务的隔离级别
（1）设置B账户中事务的隔离级别
SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
#查询事务隔离级别
SELECT @@tx_isolation;

（2）演示脏读

START TRANSACTION;
UPDATE account SET money=money-100 WHERE name='a';
UPDATE account SET money=money+100 WHERE name='b';

#查询
SELECT * FROM account;
（3）设置b账户中事务的隔离级别
SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;

（4）验证是否出现脏读
START TRANSACTION;

START TRANSACTION;
UPDATE account SET money=money-100 WHERE name='a';
UPDATE account SET money=money+100 WHERE name='b';

#查询
SELECT * FROM account;

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6.2 存储过程的创建

#建表
USE chapter06;
CREATE TABLE student(
id INT(3) PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(20) NOT NULL,
grade FLOAT,
gender CHAR(2)
);

#添加数据
INSERT INTO student(name,grade,gender)
VALUES('tom',60,'男'),
('jack',70,'男'),
('rose',90,'女'),
('lucy',100,'女');

【例6-2】
DELIMITER //
CREATE PROCEDURE Proc()
BEGIN
SELECT * FROM student;
END
//
还原
DELIMITER ;
DELIMITER //和DELIMITER ;两句，DELIMITER是分割符的意思，因为MySQL默认以";"为分隔符，如果我们没有声明分割符，
那么编译器会把存储过程当成SQL语句进行处理，则存储过程的编译过程会报错，
所以要事先用DELIMITER关键字申明当前段分隔符，
这样MySQL才会将";"当做存储过程中的代码，不会执行这些代码，
用完了之后要把分隔符还原。

【例6-3】
DECLARE s_grade FLOAT;
DECLARE s_gender CHAR(2);
SELECT grade, gender INTO s_grade, s_gender
FROM student WHERE name = 'rose';

【例6-4】
//方法一：使用sqlstate_value
DECLARE command_not_allowed CONDITION FOR SQLSTATE'42000';
//方法二：使用mysql_error_code
DECLARE command_not_allowed CONDITION FOR 1148;

【例6-5】
//方法一：捕获sqlstate_value
DECLARE CONTINUE HANDLER FOR SQLSTATE '42S02'SET @info='NO_SUCH_TABLE';

//方法二：捕获mysql_error_code
DECLARE CONTINUE HANDLER FOR 1146 SET @info='NO_SUCH_TABLE';

//方法三：先定义条件，然后调用
DECLARE no_such_table CONDITION FOR 1146;
DECLARE CONTINUE HANDLER FOR NO_SUCH_TABLE SET @info='ERROR';

//方法四：使用SQLWARNING
DECLARE EXIT HANDLER FOR SQLWARNING SET @info='ERROR';

//方法五：使用NOT FOUND
DECLARE EXIT HANDLER FOR NOT FOUND SET @info='NO_SUCH_TABLE';

//方法六：使用SQLEXCEPTION
DECLARE EXIT HANDLER FOR SQLEXCEPTION SET @info='ERROR';

【例6-6】
mysql> CREATE TABLE test.t(s1 int,primary key(s1));
Query OK, 0 rows affected (0.44 sec)

mysql> DELIMITER //
mysql> CREATE PROCEDURE demo()
-> BEGIN
-> DECLARE CONTINUE HANDLER FOR SQLSTATE '23000' SET @x2=1;
-> SET @x=1;
-> INSERT INTO test.t VALUES(1);
-> SET @x=2;
-> INSERT INTO test.t VALUES(1);
-> SET @x=3;
-> END; //
Query OK, 0 rows affected (0.09 sec)
mysql> DELIMITER ;

mysql> CALL demo();
Query OK, 0 rows affected (0.08 sec)

mysql> SELECT @x ;
+------+
| @x |
+------+
| 3 |
+------+
1 row in set (0.00 sec)

【例6-7】
CASE val
WHEN 1 THEN SELECT 'val is 1';
WHEN 2 THEN SELECT 'val is 2';
ELSE SELECT 'val is not 1or 2';
END CASE;

【例6-8】
DECLARE id INT DEFAULT 0;
add_loop:LOOP
SET id=id+1;
IF id>=10 THEN LEAVE add_loop;
END IF;
END LOOP add_loop;

【例6-9】
CREATE PROCEDURE doiterate()
BEGIN
DECLARE p1 INT DEFAULT 0;
my_loop:LOOP
SET p1=p1+1;
IF p1<10 THEN ITERATE my_loop;
ELSEIF p1>20 THEN LEAVE my_loop;
END IF;
SELECT 'p1 is between 10 and 20';
END LOOP my_loop;
END

【例6-10】
DECLARE id INT DEFAULT 0;
REPEAT
SET id=id+1;
UNTIL id>=10;
END REPEAT;

【例6-11】
DECLARE i INT DEFAULT 0;
WHILE i <10 DO
SET i=i+1;
END WHILE;

【例6-12】
1、定义存储过程：
DELIMITER //

CREATE PROCEDURE CountProc1(IN s_gender VARCHAR(50),OUT num INT)

BEGIN

SELECT COUNT(*) INTO num FROM student WHERE gender = s_gender;

END //

DELIMITER ;
2、调用存储过程：
CALL CountProc1("女",@num);
3、查看返回结果：
SELECT @num;

【例6-13】
SHOW PROCEDURE STATUS LIKE'C%'G

【例6-14】
SHOW CREATE PROCEDURE chapter06.CountProc1G

【例6-15】
ALTER PROCEDURE CountProc1
MODIFIES SQL DATA
SQL SECURITY INVOKER;

#从information_schema.Routines表中查看存储过程的信息

SELECT * FROM information_schema.Routines
WHERE ROUTINE_NAME='CountProc1' AND ROUTINE_TYPE='PROCEDURE

【例6-16】
DROP PROCEDURE CountProc1;
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6.4 综合案例—存储过程应用

#建表
CREATE TABLE stu(id INT,name VARCHAR(50),class VARCHAR(50));
INSERT INTO stu VALUE (1,'Lucy','class1'),(2,'Tom','class1'),(3,'Rose','class2');

#创建存储过程
CREATE PROCEDURE addcount(out count INT)
BEGIN
DECLARE itmp INT;
DECLARE cur_id CURSOR FOR SELECT id FROM stu;
DECLARE EXIT HANDLER FOR NOT FOUND CLOSE cur_id;
SELECT count(*) INTO count FROM stu;
SET @sum=0;
OPEN cur_id;
REPEAT
FETCH cur_id INTO itmp;
IF itmp<10
THEN SET @sum= @sum+itmp;
END IF;
UNTIL 0 END REPEAT;
CLOSE cur_id;
END ;