当前位置: X题卡 > 所有题目 > 题目详情

设有关系R(A,B,C)和S(C,D)与SQL语句SELECT A,B,D FROM R,S WHERE R.C=S.C等价的关系代数表达式是( )。

查看本题答案

你可能感兴趣的试题

GROUP BY grade  GROUP BY sno  ORDER BY grade  ORDER BY sno  
SEI,ECT sno FROM SC WH ERE grade BETWEEN O AND 60  SELECT sno FROM SC WHERE grade<60  SELECT sno FROM SC HAVlNG grade BETWEEN O AND 60  SELECT sno FROM SC HAVING grade<60  
GROUP BY grade  GROUP BY sno  ORDER BY grade  ORDER BY sno  
SELEC..FRO..WHERE  SELEC..WHER..FROM  SELEC..WHER..GROUP BY  SELEC..FRO..ORDER BY  
OR.C=SCA,B,D(R×S))  ЛA,B,DR.C=SC(R×S))  σR.C=SC((ЛA,BR)×(ЛDS))  σR.C=SCDA,BR)×S))  

热门试题

更多