有表结构如下: CREATE TABLE `test` ( `a` int(11) NOT NULL, `b` int(11) DEFAULT NULL, `c` int(11) DEFAULT NULL, PRIMARY KEY (`a`), KEY `idx1` (`c`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 +---+------+------+ | a | b | c | +---+------+------+ | 1 | 1 | 1 | | 2 | 2 | 2 | | 3 | 3 | 3 | +---+------+------+ 下面有A,B两个连接开启的事务: A连接 B连接 begin begin update test set c = 15 where a = 1 ; update test set c = 12 where a = 2 ; update test set b = 15 where b = 1 ; update test set c = 12 where a = 3 ; update test set b = 15 where b = 1 ; 下面描述正确的是:
A、B连接的第一个update不会被阻塞
B、A连接的第二个update会被阻塞
C、B连接的第二个update会被阻塞
D、B连接的第三个update不会被阻塞
A、(100,100,10.5)
B、(100,101,10.5)
C、(100,100,10.50)
D、语句无法执行
创建测试数据 成绩表 SC create table SC(SId varchar(10),CId varchar(10),score decimal(18,1)) insert into SC values('01' , '01' , 80); insert into SC values('01' , '02' , 90); insert into SC values('01' , '03' , 99); insert into SC values('02' , '01' , 70); insert into SC values('02' , '02' , 60); insert into SC values('02' , '03' , 80); insert into SC values('03' , '01' , 80); insert into SC values('03' , '02' , 80); insert into SC values('03' , '03' , 80); insert into SC values('04' , '01' , 50); insert into SC values('04' , '02' , 30); insert into SC values('04' , '03' , 20); insert into SC values('05' , '01' , 76); insert into SC values('05' , '02' , 87); insert into SC values('06' , '01' , 31); insert into SC values('06' , '03' , 34); insert into SC values('07' , '02' , 89); insert into SC values('07' , '03' , 98);
A、INSERT INTO SC VALUES('200823','101',NULL,NULL);
B、INSERT INTO SC VALUES('201009','111',60,必修);
C、INSERT INTO SC VALUES(NULL,'103',80,'选修');
D、INSERT INTO SC VALUES('201132',NULL,86,'');
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