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select * from tab ...

[单选题]
select * from tab where colA=’1’ union select * from tab where colB=’2’ 与此查询语句等价的选项是
  • select * from tab where colA=’1’ and colB= ’2’
  • select * from tab where colA=’1’ or colB= ’2’
  • select * from tab where colA=’1’
  • select * from tab where colB=’2’
B UNION求并并去重
发表于 2019-09-10 15:51:46 回复(0)