A.除is [not] null之外,空值满足任何查找条件
B.如果null参与比较运算,有些情况下是可以判断为真的或为假的。
C.如果null参与聚集运算,则除count(*)之外其它聚集函数都忽略null
D.如果null参与算术运算,则该算术表达式的值为null
第1题
第2题
第4题
A、Select S1.S# From SC S1, SC S2 Where S1.S# = S2.S# and S1.C#=‘001’ and S2.C#=‘002’ and S1.Score > S2.Score;
B、Select S1.S# From SC S1, SC S2 Where S1.S# = S2.S# and S1.C#=‘001’ and S2.C#=‘002’ and S2.Score > S1.Score;
C、Select S1.S# From SC S1, SC S2 Where S1.S# = S2.S# and S1.C#=‘001’ and S2.C#=‘002 ;
D、Select * From SC S1, SC S2 Where S1.S# = S2.S# and S1.C#=‘001’ and S2.C#=‘002’ and S1.Score > S2.Score;
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