如何减少由子字符串和instring引起的代码重复？

Question

我需要将一个以’\
n’分隔的文本字段（描述）解析为三个单独的字段。我通过利用substr和来执行此操作instr，但是它导致难以阅读和重复的sql。有没有一种方法可以创建和使用变量或表达式来保存instring函数返回的“位置”值，因此我可以将该变量传递给它substr？我在下面发布的代码可以正常工作并返回正确的结果，但是感觉不正确。有很多重复。

相关原始数据：

DBKEY       DBTIME                      DBUSER     DESCRIPTION
40846809    2013-11-18 11:04:11.0000000 abc$userid  The following Message List entry has been logged:\nError Number:5011\nDescription:Planogram: 60E90001006.0SMA :: UPC:  is not numeric\nSeverity:0
40846810    2013-11-18 11:04:11.0000000 abc$userid  The following Message List entry has been logged:\nError Number:5000\nDescription:Planogram: 60E90001006.0SMA :: ID: NEW  not 9 digits\nSeverity:0
40846811    2013-11-18 11:04:11.0000000 abc$userid  The following Message List entry has been logged:\nError Number:5001\nDescription:Planogram: 60E90001006.0SMA :: ID: NEW  not numeric\nSeverity:0

所需结果：

DBKEY       DBTIME                      USERID  ERROR_NUM   DESCRIPTION SEVERITY
40846809    2013-11-18 11:04:11.0000000 userid  5011        Planogram: 60E90001006.0SMA :: UPC:  is not numeric 0
40846810    2013-11-18 11:04:11.0000000 userid  5000        Planogram: 60E90001006.0SMA :: ID: NEW  not 9 digits    0
40846811    2013-11-18 11:04:11.0000000 userid  5001        Planogram: 60E90001006.0SMA :: ID: NEW  not numeric 0
40846812    2013-11-18 11:04:11.0000000 userid  5003        Planogram: 60E90001006.0SMA :: ID: NEW  ID must begin with 000,200,220,900,950,990,or 999   0

当前代码：

SELECT DBKEY,DBTIME,
        SUBSTR(DBUSER,INSTR(DBUSER,'$',1,1)+1) AS USERID,
        SUBSTR(ERROR_NUM,INSTR(ERROR_NUM,':')+1) AS ERROR_NUM,
        SUBSTR(DESC1,INSTR(DESC1,':')+1) AS DESCRIPTION,
        SUBSTR(SEVERITY,INSTR(SEVERITY,':')+1) AS SEVERITY
FROM(
    SELECT l.DBKEY,DBTIME,DBUSER,
        --substring(description,first+2,second-first-2)
        SUBSTR(DESCRIPTION,INSTR(DESCRIPTION,'\n',1,1)+2,INSTR(DESCRIPTION,'\n',1,2)-INSTR(DESCRIPTION,'\n',1,1)-2) AS ERROR_NUM,
        --substring(description,second+2,third-second-2)
        SUBSTR(DESCRIPTION,INSTR(DESCRIPTION,'\n',1,2)+2,INSTR(DESCRIPTION,'\n',1,3)-INSTR(DESCRIPTION,'\n',1,2)-2) AS DESC1,
        --substring(description,third+2) 
        SUBSTR(DESCRIPTION,INSTR(DESCRIPTION,'\n',1,3)+2) AS SEVERITY
        /*,
        INSTR(DESCRIPTION,''\n'',1,1) as first,
        INSTR(DESCRIPTION,''\n'',1,2) as second,
        INSTR(DESCRIPTION,''\n'',1,3) as third,
        */
    FROM EVENT_LOG l
)derivedtbl

Answer 1

我建议使用REGEXP_SUBSTR哪一个功能可以达到预期的效果：

SELECT
    l.DBKEY,
    l.DBTIME,
    REGEXP_SUBSTR(l.DBUSER, '[^$]+$')                 AS USERID,
    REGEXP_SUBSTR(l.DESCRIPTION, '[0-9]{4}')          AS ERROR_NUM,
    REPLACE(REGEXP_SUBSTR(l.DESCRIPTION, 'Planogram:[^\]+\\n'), '\n', '')
                                                      AS DESCRIPTION,
    REGEXP_SUBSTR(l.DESCRIPTION, '\d+$')              AS SEVERITY
FROM
    EVENT_LOG l;

我已经创建并测试了SQLFiddle。有关更多信息，REGEXP_SUBSTR您可能需要阅读Oracle
Docs
。