mysql数据表之间求余集

//数据表之间有相同类型的数据列求余集(数据表见图) mysql> (SELECT a.id FROM etl02 a LEFT OUTER JOIN etl01 b ON a.id = b.id WHERE b.id is null)     -> UNION     -> (SELECT c.id FROM etl01 c LEFT OUTER JOIN etl02 d ON c.id = d

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