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mysql数据库 时间：2024-12-25 09:55:54
作者：文/会员上传
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select sum(a.b) as num from (select count() as b from table_1 union all select count() as b from table_2) as a（注意这里要取个别名）
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select sum(a.b) as num from (
select count() as b from table_1
union all
select count() as b from table_2
) as a（注意这里要取个别名）
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