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关系代数表达式R×S÷T-U的运算结果是（）
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关系RS如下图所示关系代数表达式π453σ1＜6R×S的输出结果与等价该表达式与等价若对关系R
A
B
C
D
设R和S是两个关系与关系代数表达式R×S等价的SQL语句是【2】
设R和S是两个关系与关系代数表达式R*S等价的SQL语句是【14】
设r和s是两个关系与关系代数表达式r×s等价的SQL语句是______
设r和s是两个关系与关系代数表达式r×s等价的SQL语句是【13】
假设关系RST如下表所示关系代数表达式T=S= 关系代数表达式T=
R∩S
R∪S
R×S
R／S
设R和S是两个关系与关系代数表达式R×S等价的SQL语句是【8】
设有如下关系 与元组演算表达式t|uvRu∧SvAu[3]=v[1]∧u[4
πA,B (σA＞E (R
S))
πB (σA＞E (R×S))
πB (σA＞E (R
S))
πB (σR.C=S.C∧A＞E (R×S))
设有如下关系与元组演算表达式 等价的关系代数表达式是关系代数表达式R÷S的
设R和S是两个关系与关系代数表达式R×S等价的SQL语句是select*
设有如下关系与元组演算表达式 等价的关系代数表达式是关系代数表达式R÷S的
设R和S是两个关系与关系代数表达式R×s等价的SQL语句是select*
设R和S是两个关系与关系代数表达式R×S等价的SQL语句是【8】
设R和S是两个关系与关系代数表达式R×S等价的SQL语句是【】
关系代数表达式R×S÷T-U的运算结果是
A
B
C
D
设有如下关系 与元组演算表达式 t| u vRu Sv u
A
B
C
D
设R和S是两个关系与关系代数表达式R*S等价的SQL语句是【】
设有如下关系 与元组演算表达式t|uvRu∧SvAu[3]=v[1]∧u[4
A
B
C
D
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S)) πB (σA＞E (R×S)) πB (σA＞E (RS)) πB (σR.C=S.C∧A＞E (R×S))
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