Oracle - 当我使用 EXISTS 时，关系运算符无效

Posted 2023-03-28

【中文标题】Oracle - 当我使用 EXISTS 时，关系运算符无效

【英文标题】：Oracle - Invalid relational operator when I'm using EXISTS

【发布时间】：2020-05-01 18:04:23

【问题描述】：

我收到了以下查询，当满足条件时，从表 et_fact_reclam_ter_his_misc 中删除返回的记录：

DELETE FROM et_fact_reclam_ter_his_misc
 WHERE num_siniest || num_exped IN
 (SELECT DISTINCT num_siniest || num_exped
          FROM et_fact_reclam_ter_his_misc t1
         WHERE NOT EXISTS (SELECT *
                  FROM et_fact_reclam_ter_misc t2
                 WHERE t1.num_siniest = t2.num_siniest));

我一直在搜索，发现使用EXISTS而不是IN会提高查询性能。但是我遇到了2个错误。第一个是当我将IN 运算符替换为EXISTS 时出现的错误消息：

DELETE FROM et_fact_reclam_ter_his_misc
 WHERE num_siniest || num_exped EXISTS
 (SELECT DISTINCT num_siniest || num_exped
          FROM et_fact_reclam_ter_his_misc t1
         WHERE NOT EXISTS (SELECT *
                  FROM et_fact_reclam_ter_misc t2
                 WHERE t1.num_siniest = t2.num_siniest));


ORA-00920: invalid relational operator

第二个是当我尝试在DELETE 内嵌套一个SELECT，但返回的行数不同：

DELETE FROM et_fact_reclam_ter_his_misc
 WHERE EXISTS
 (SELECT FROM et_fact_reclam_ter_his_misc
         WHERE num_siniest || num_exped IN
               (SELECT DISTINCT num_siniest || num_exped
                  FROM et_fact_reclam_ter_his_misc t1
                 WHERE NOT EXISTS
                 (SELECT *
                          FROM et_fact_reclam_ter_misc t2
                         WHERE t1.num_siniest = t2.num_siniest)));

感谢任何有助于提高查询性能的帮助

【问题讨论】：

如果您可以随约束/索引一起描述表格，则可以即兴创作。还需要每个表中的记录数和被删除的记录数

您可以尝试每个查询和反馈。

我一直在搜索，发现使用 EXISTS 代替 IN 可以提高查询性能。 你从哪里读到的？不会的。

【参考方案1】：

您可以尝试下面的方法，而不是连接字段以进行连接的最佳方法，

DELETE FROM et_fact_reclam_ter_his_misc A
 WHERE EXISTS
 (  SELECT 1 FROM 
         (SELECT DISTINCT num_siniest || num_exped
          FROM et_fact_reclam_ter_his_misc t1) B
          WHERE A.num_siniest|| A.num_exped = B.num_siniest || B.num_exped 
         AND NOT EXISTS (SELECT 1
                  FROM et_fact_reclam_ter_misc t2
                 WHERE B.num_siniest = t2.num_siniest));

似乎连接的列是数字，它会强制 oracle 将其强制转换为 char，这可能会影响性能。如果您要处理大量记录，那么下面的列应该会更快。

DELETE FROM et_fact_reclam_ter_his_misc A
 WHERE EXISTS
 (  SELECT 1 FROM 
         (SELECT DISTINCT num_siniest, num_exped
          FROM et_fact_reclam_ter_his_misc t1) B
          WHERE A.num_siniest = B.num_siniest
          AND  A.num_exped = B.num_exped 
         AND NOT EXISTS (SELECT 1
                  FROM et_fact_reclam_ter_misc t2
                 WHERE B.num_siniest = t2.num_siniest));

DISTINCT 会矫枉过正，用 group by 代替肯定会好得多，所以最好的是：

DELETE FROM et_fact_reclam_ter_his_misc A
 WHERE EXISTS
 (  SELECT 1 FROM 
         (SELECT num_siniest, num_exped,count(1)
          FROM et_fact_reclam_ter_his_misc t1
          group by num_siniest, num_exped) B
          WHERE A.num_siniest = B.num_siniest
          AND  A.num_exped = B.num_exped 
         AND NOT EXISTS (SELECT 1
                  FROM et_fact_reclam_ter_misc t2
                 WHERE B.num_siniest = t2.num_siniest));

【参考方案2】：

看起来可以这样做：

delete et_fact_reclam_ter_his_misc t1
where  not exists
       ( select * from et_fact_reclam_ter_misc t2
         where  t2.num_siniest = t1.num_siniest
       );

在原始版本中，第一级子查询似乎是在查询被删除的同一张表，只是为了构造一个not exists 子查询。我怀疑您要做的就是删除主表中不存在num_siniest 的his 行。一些示例数据和预期结果会让这一点更清楚。