Oracle SQL开发人员使用始终“ true”条件是从子句中删除。（xxx“ null或xxx”不是零）

发布于 2025-01-30 12:10:32 字数 413 浏览 2 评论 0原文

我今天使用的是Oracle SQL开发人员版本19.2.1.247，并使用图形方式删除了几行。我的意思是，我选择了行，然后按红色X十字以删除所选的行。它奏效了，一切都很好。排除行。

但是，我看看日志并发现了这一点：

DELETE FROM "DB"."PERSONS" WHERE ROWID = 'AADG' AND ORA_ROWSCN = '5196' and ( "ID" is null or "ID" is not null )

嗯，我不明白最后一个陈述。

"ID" is null or "ID" is not null

在我看来，显然，这永远是真实的。我对知道这个Oracle SQL开发人员添加此内容的原因感到好奇。为什么使用？何时该陈述是不正确的？

原文

I was using today Oracle SQL Developer version 19.2.1.247 and removed couple of rows using the graphical way. I mean, I selected the row and press the red x cross to remove the selected rows.
It worked, all fine. Rows were removed.

However, I took a look to the logs and find out this:

DELETE FROM "DB"."PERSONS" WHERE ROWID = 'AADG' AND ORA_ROWSCN = '5196' and ( "ID" is null or "ID" is not null )

Well, I don't understand the last statement.

"ID" is null or "ID" is not null

To my eyes, apparently, this is always going to be true. I feel curiosity about knowing the reason why this Oracle SQL Developer is adding this. Why is this used? When this statement will not be true?

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月依秋水 2025-02-06 12:10:33

可能只是一个异常，但它不会对声明的执行（或性能）产生任何影响。例如，我做到了：

SQL> create table t as select * from scott.emp;

Table created.

然后删除了SQL Dev中的一行，屈服

DELETE FROM "T" WHERE ROWID = 'AAZRaiABAAAA5eLAAL' 
AND ORA_ROWSCN = '16330866545209' 
and ( "EMPNO" is null or "EMPNO" is not null )

，优化器提出了这一点：

------------------------------------------------------------------------------------
| Id  | Operation                   | Name | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------
|   0 | DELETE STATEMENT            |      |     1 |    12 |     1   (0)| 00:00:01 |
|   1 |  DELETE                     | T    |       |       |            |          |
|*  2 |   TABLE ACCESS BY USER ROWID| T    |     1 |    12 |     1   (0)| 00:00:01 |
------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - filter("ORA_ROWSCN"=16330866545209)

简单地忽略了冗余谓词。

我的表没有索引或主键，因此看起来只会从表中从表中获取第一列。

Probably just an anomaly, but it wont have any impact on the execution (or performance) of the statement. For example, I did:

SQL> create table t as select * from scott.emp;

Table created.

and then deleted a row in SQL Dev, yielding

DELETE FROM "T" WHERE ROWID = 'AAZRaiABAAAA5eLAAL' 
AND ORA_ROWSCN = '16330866545209' 
and ( "EMPNO" is null or "EMPNO" is not null )

and the optimizer came up with this:

------------------------------------------------------------------------------------
| Id  | Operation                   | Name | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------
|   0 | DELETE STATEMENT            |      |     1 |    12 |     1   (0)| 00:00:01 |
|   1 |  DELETE                     | T    |       |       |            |          |
|*  2 |   TABLE ACCESS BY USER ROWID| T    |     1 |    12 |     1   (0)| 00:00:01 |
------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - filter("ORA_ROWSCN"=16330866545209)

The redundant predicates were simply ignored.

My table had no indexes or primary keys, so it would appear the simply takes the first column from the table for this predicate.

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