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无级联调度应满足:对于每对事务T1和T2,如果T2读取了由T1所写的数据项,则T1必须在T2这一读取前 【】
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A.SELECT * FROM T1 MINUS SELECT * FROM T2
B.SELECT * FROM T1 EXCEPT SELECT * FROM T2
C.SELECT * FROM T2 UNION EXCEPT SELECT * FROM T1
D.SELECT * FROM T1 NOT EXISTS SELECT * FROM T2
A.template <T1,T2>
B.template <class T1,T2>
C.template <class T1,class T2>
D.template <typename T1;typename T2>
A.t1=t2
B.t1<t2
C.t1>t2
D.不能判断
A.SELECT * FROM t1 UNION SELECT * FROM t2
B.SELECT * FROM t1 UNION DISTINCT SELECT * FROM t2
C.SELECT * FROM t1 INTERSECT SELECT * FROM t2
D.SELECT * FROM t1 WHERE (c1,c2)= (SELECT c1,c2 FROM t2)
A.T1的属性个数等于T2的属性个数
B. T1的属性个数小于T2的属性个数
C. T1的属性个数大于或等于T2的属性个数
D. T1的属性个数大于T2的属性个数
A.并发处理
B.封锁
C.循环
D.死锁
A.变压器T1的功率大于变压器T2的功率;
B.变压器T1的功率小于变压器T2的功率;
C.变压器T1和变压器T2的功率相等;
D.不能确定,还需其他条件。