Question

我有以下SQL：

Select MyNumber
FROM (SELECT to_number(Name) AS MyNumber
    FROM TableA
    WHERE regexp_replace(Name, '\d+') IS NULL)

该查询应该通过检查是否保留了所有数字（如果所有数字都替换为空）来从TableA中过滤掉非数字名称。

有人可以解释为什么当我将以下WHERE条件添加为外部WHERE时为什么得到“无效数字”-异常：

WHERE MyNumber IS NULL

MyNumber是什么类型？特别是，我也想知道，当我取消条件时为什么没有出现错误：

WHERE NOT MyNumber IS NULL

在此先感谢您的帮助。

Answer 1

我可以复制您所看到的内容，但是出现is null 或 is not null错误：

create table tablea (name) as
select '123' from dual
union all select 'abc123' from dual
union all select 'abc123def456,' from dual
union all select '1abc123def456,' from dual;

SELECT MyNumber
FROM (
  SELECT to_number(Name) AS MyNumber
  FROM TableA
  WHERE regexp_replace(Name, '\d+') IS NULL
);

  MYNUMBER
----------
       123

SELECT MyNumber
FROM (
  SELECT to_number(Name) AS MyNumber
  FROM TableA
  WHERE regexp_replace(Name, '\d+') IS NULL
)
WHERE mynumber IS NULL;

ORA-01722: invalid number

SELECT MyNumber
FROM (
  SELECT to_number(Name) AS MyNumber
  FROM TableA
  WHERE regexp_replace(Name, '\d+') IS NULL
)
WHERE mynumber IS NOT NULL;

ORA-01722: invalid number

您也许可以添加提示以使其以不同的方式处理，但是您可以添加另一个正则表达式，这样可以使转换成功的任何非数字值都不会引起问题：

SELECT MyNumber
FROM (
  SELECT to_number(regexp_replace(Name, '[^[:digit:]]')) AS MyNumber
  FROM TableA
  WHERE regexp_replace(Name, '[[:digit:]]+') IS NULL
);

  MYNUMBER
----------
       123

SELECT MyNumber
FROM (
  SELECT to_number(regexp_replace(Name, '[^[:digit:]]')) AS MyNumber
  FROM TableA
  WHERE regexp_replace(Name, '[[:digit:]]+') IS NULL
)
WHERE mynumber IS NULL;

no rows selected

SELECT MyNumber
FROM (
  SELECT to_number(regexp_replace(Name, '[^[:digit:]]')) AS MyNumber
  FROM TableA
  WHERE regexp_replace(Name, '[[:digit:]]+') IS NULL
)
WHERE mynumber IS NOT NULL;

  MYNUMBER
----------
       123

正如@MrLlama指出的那样，使用regexp_like会更干净一些：

SELECT MyNumber
FROM (
  SELECT to_number(regexp_replace(Name, '[^[:digit:]]')) AS MyNumber
  FROM TableA
  WHERE regexp_like(Name, '^[[:digit:]]+$')
);

获得相同的结果（包括原始错误）。

Answer 2

查询应该从TableA中过滤掉非数字名称

您为什么不使用这样的东西呢？

SQL> with test (name) as
  2    (select '12345'     from dual union
  3     select 'abc123'    from dual union
  4     select 'lksfj'     from dual union
  5     select 'ping pong' from dual
  6    )
  7  select name
  8  from test
  9  where regexp_like(name, '^\d+$');

NAME
---------
12345

SQL>

这可能需要一些调整，具体取决于NAME列的内容。

Oracle ORA-01722：无效的数字错误，因为WHERE IS NULL条件

2 个答案: