mysql - 我如何知道哪些事务首先运行

Question

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE

INSERT INTO Students VALUES(’Jason’,50);

UPDATE Students SET mark = mark + 10;

COMMIT

SET TRANSACTION ISOLATION READ COMMITED

INSERT INTO Students VALUES (’Kylie’,70);

SELECT SUM(mark) FROM Students;

COMMIT

如果我有两个同时运行的事务，我如何知道哪个事务首先运行以及查询将返回哪些值？我知道 Serialized 隔离了 T1。但更重要的是我不知道如何继续。

Answer 1

如果同时运行两者，READ COMMITTED 将等待 SERIALIZABLE 完成。顺便说一句，您的 TSQL 上似乎缺少 BEGIN TRANSACTION。

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE
BEGIN TRANSACTION
   INSERT INTO Students VALUES(’Jason’,50);
   UPDATE Students SET mark = mark + 10;
COMMIT TRANSACTION

SET TRANSACTION ISOLATION READ COMMITTED
BEGIN TRANSACTION
   INSERT INTO Students VALUES (’Kylie’,70);
   SELECT SUM(mark) FROM Students;
COMMIT TRANSACTION