将一行数据变为多行，例如：

原始写法，效率很低,特别是数据量稍微大点时基本就跑不出来了

SELECT REGEXP_SUBSTR(A.ORDERID,'[^,]+', 1, LEVEL) AS ORDERID
FROM
        (
                SELECT  ORDERID
                FROM    orders
                WHERE   INSTR(ORDERID,',')>0
                        AND BILLTYPE      =1004
                        AND NVL(STATUS,0) =0
                        AND PERMIT        =1
        )
A CONNECT BY REGEXP_SUBSTR(A.ORDERID, '[^,]+', 1, LEVEL) IS NOT NULL

ORDERID
--------------------------------------------------------------------------------
89970,89962
90154,90145
90186,90187

优化后的写法

select distinct regexp_substr(t1.ORDERID, '[^,]+', 1, level) as ORDERID
from (SELECT id,ORDERID
      FROM orders
      WHERE INSTR(ORDERID,',')>0
        AND BILLTYPE      =1004
        AND NVL(STATUS,0) =0
        AND PERMIT        =1
    ) t1
connect by t1.ID = prior t1.ID
and prior dbms_random.value is not null
and level <= length(t1.ORDERID) - length(regexp_replace(t1.ORDERID, ',', '')) + 1 ;

ORDERID
--------------------------------------------------------------------------------
89962
89970
90145
90154
90186
90187