regex - Oracle REGEXP 仅替换第一个字符

Question

在下面的示例中：

WITH X(DATA, ORD)
AS
(         
Select '@asdf@'   , 01 FROM DUAL UNION
Select '\qw@er\'  , 02 FROM DUAL UNION
Select '-zxcv-@' , 03  FROM DUAL UNION
Select '_poiu@' ,  04 FROM DUAL 
)

SELECT
REGEXP_REPLACE(DATA, '[@\-_]', '', 1)
FROM X
ORDER BY ORD;  
;  

我得到这个回应：

asdf 
qwer
-zxcv- 
poiu

但我想替换“@”、“\”、“-”或“_”，前提是它是字符串上的第一个字符，而不是中间。另外，它不适用于“-”字符。

Answer 1

以下正则表达式应该可以工作：^[@\\_-]. 请注意，破折号-必须是字符类中的最后一个字符。

WITH X AS (
  SELECT '@asdf@' AS data, 01 AS ord FROM DUAL UNION
  SELECT '\qw@er\', 02 FROM DUAL UNION
  SELECT '-zxcv-@', 03  FROM DUAL UNION
  SELECT '_poiu@',  04 FROM DUAL 
)
SELECT REGEXP_REPLACE(DATA, '^[@\\_-]')
 FROM X
ORDER BY ORD

Answer 2

相反，使用这个

REGEXP_REPLACE(DATA, '^[@|\\|-|_]', '', 1)

注意^指定字符串开头的字符。

查询

WITH X(DATA, ORD)
AS
(         
Select '@asdf@'   , 01 FROM DUAL UNION
Select '\qw@er\'  , 02 FROM DUAL UNION
Select '-zxcv-@' , 03  FROM DUAL UNION
Select '_poiu@' ,  04 FROM DUAL 
)
SELECT
REGEXP_REPLACE(DATA, '^[@|\\|-|_]', '', 1)
FROM X
ORDER BY ORD; 

给了我结果

asdf@, qw@er, zxcv@, poiu@,