Remove all characters after a specific character in PL/SQL

问题

How do I get a substring from this example value:

 john.abc_1234

I want it to return john.abc.So basically we need to remove all the information after _.

More examples: 1234_abc

回答1:

You can use SUBSTR and INSTR:

select substr('john.abc_1234', 1, instr('john.abc_1234', '_') -1)
from dual

Warning: This is only guaranteed to work if your string actually has an underscore in it

Update

Additionally, if you are running from Oracle 10g on, you could take the Regex path, which would more powerfully handle exceptions.

Here are some links on how to do it in Oracle:

http://psoug.org/reference/regexp.html
http://psoug.org/snippet/Regular-Expressions--Regexp-Cheat-Sheet_856.htm
http://www.regular-expressions.info/oracle.html

回答2:

You can use this monstrosity, when you're not sure if all your values contain the character you want to cut off your string at.

SELECT
    (CASE WHEN INSTR(field, '_') > 0
        THEN substr(field, 1, instr(field, '_') -1)
        ELSE field
    END) AS field
FROM
    dual

回答3:

This guy figured it out! http://programcsharp.com/blog/post/strip-non-numeric-characters-from-a-string-in-sql-server

SELECT
    (SELECT CAST(CAST((
        SELECT SUBSTRING(FieldToStrip, Number, 1)
        FROM master..spt_values
        WHERE Type='p' AND Number <= LEN(FieldToStrip) AND
            SUBSTRING(FieldToStrip, Number, 1) LIKE '[0-9]' FOR XML Path(''))
    AS xml) AS varchar(MAX)))
FROM
    SourceTable

来源：https://stackoverflow.com/questions/7717566/remove-all-characters-after-a-specific-character-in-pl-sql

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