实际数据
data dataflag
aaa 1
aaa 2
aaa 3
aaab 3
dsab 3
casscab 2
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select * from testtable order by case when dataflag=2 then 0 when dataflag=1 then 1 when dataflag=3 then 2 end
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casscab 2
aaa 2
aaa 1
aaa 3
aaab 3
dsab 3
order by 对结果进行排序，case when then end用作于条件控制，二者混合使用就可以使结果指定顺序进行输出