单项选择题
如果要查询rankID字段值为空,则在WHERE字句的条件应该写成()
A.rankID=NULL
B.rankID==NULL
C.rankID IS NOT NULL
D.rankID IS NULL
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单项选择题
A.rankID=NULL
B.rankID==NULL
C.rankID IS NOT NULL
D.rankID IS NULL
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