是否删除sql查询中的重复项？

我有下面的sql查询。我正在使用oracle 10g。在这里，我结合了两个查询的结果

select distinct combined.some_id from (
  SELECT DISTINCT l.some_id FROM tableA l where
        l.some_code  ='ABC' and l.code_two IN('S','H')
        union all  
        SELECT DISTINCT e.some_id FROM tableA_Replica e where
        e.some_code  ='ABC' and e.code_two IN('S','H') and e.some_id NOT IN ( SELECT DISTINCT l.some_id FROM tableA l where
        l.some_code  ='ABC' and l.code_two IN('S','H'))
    ) combined,tableA_Replica_join_table_ONE x where 
        combined.some_id = x.some_id(+)
        AND (x.status   IN('ACTIVE','INACTIVE'))


        UNION

select distinct combined.some_id from (
  SELECT DISTINCT l.some_id FROM tableA l where
        l.some_code  ='ABC' and l.code_two IN('S','H')
        union all  
        SELECT DISTINCT e.some_id FROM tableA_Replica e where
        e.some_code  ='ABC' and e.code_two IN('S','H') and e.some_id NOT IN ( SELECT DISTINCT l.some_id FROM tableA l where
        l.some_code  ='ABC' and l.code_two IN('S','H'))
    ) combined,tableA_Replica_join_table_TWO x where 
        combined.some_id = x.some_id(+)
        AND (x.status   IN('ACTIVE','INACTIVE')) 

在这两个查询中，下面的部分是常见的

SELECT DISTINCT l.some_id FROM tableA l where
        l.some_code  ='ABC' and l.code_two IN('S','H')
        union all  
        SELECT DISTINCT e.some_id FROM tableA_Replica e where
        e.some_code  ='ABC' and e.code_two IN('S','H') and e.some_id NOT IN ( SELECT DISTINCT l.some_id FROM tableA l where
        l.some_code  ='ABC' and l.code_two IN('S','H'))

---

如何避免两个查询中的代码重复

您可以使用公共表表达式（CTE，有时也称为“WITH语句”）：

---

此查询删除了大量重复项：

select distinct combined.some_id from (
        SELECT distinct l.some_id FROM tableA
           union
        SELECT distinct e.some_id FROM tableA_Replica
    ) combined
    inner join (
        select x.status, x.some_id from tableA_Replica_join_table_ONE x 
             union
        select y.status, y.some_id from tableA_Replica_join_table_TWO y 
    ) join_table
    on combined.some_id = join_table.some_id(+) and
       join_table.status IN('ACTIVE','INACTIVE') and
       combined.some_code  ='ABC' and l.code_two IN('S','H')

什么样的查询最好取决于数据的结构

有一件事你绝对不需要做：

SELECT DISTINCT l.some_id FROM tableA l where
        l.some_code  ='ABC' and l.code_two IN('S','H')
        union all  
        SELECT DISTINCT e.some_id FROM tableA_Replica e where
        e.some_code  ='ABC' and e.code_two IN('S','H') and e.some_id NOT IN ( SELECT DISTINCT l.some_id FROM tableA l where
        l.some_code  ='ABC' and l.code_two IN('S','H'))

在第二个查询中，您不需要该

not IN

子句。只需使用

union

而不是

union all

——它会自动删除重复项

要考虑的另一件事是：您在许多地方使用了

distinct

。你真的需要这些吗？有些人似乎在任何地方都使用

distinct

来防止重复。然而，这是低效的，如果您不确切知道它在做什么，可能会导致细微的错误

---

通常，仅当您明确决定需要从特定查询中删除重复项时，才使用

distinct

。（如果不查看您的数据，就不可能知道您是否需要所有这些数据，但它们的数量之多让我产生怀疑）。

非常感谢您的回复。查询正在运行。在with子句中，我在这里进行两个查询的并集，如何按某个id添加顺序？请帮助我……@user1016403：如果您想对联合的结果进行排序，您可以执行

SELECT*FROM（…联合…）ORDER BY col

SELECT DISTINCT l.some_id FROM tableA l where
        l.some_code  ='ABC' and l.code_two IN('S','H')
        union all  
        SELECT DISTINCT e.some_id FROM tableA_Replica e where
        e.some_code  ='ABC' and e.code_two IN('S','H') and e.some_id NOT IN ( SELECT DISTINCT l.some_id FROM tableA l where
        l.some_code  ='ABC' and l.code_two IN('S','H'))