flysun0311

摘要： 1. UNION A∪B的逻辑,当遇到数据集中重复的行时，紧保留一个2. UNION ALL A∪B的逻辑，但与UNION不同的是，当遇到两个数据集中重复的行时，全部保留3. INTERSECT A∩B的关系,不支持INTERSECT ALL4.EXCEPT 实现A-B的关系,不支持 EXCEPT ALL测试代码：SELECT 1 AS Value1, 1 AS Value2 INTO #T1UNION ALLSELECT 1 AS Value1, 1 AS Value2UNION ALLSELECT 2 AS Value1, 2 AS Value2UNION ALLSELECT 2 ... 阅读全文