Oracle-分割字符串前字符后字符sql

Oracle-分割字符串前字符后字符sql
regexp_instr：函数它返回一个整数，指示开始或结束匹配的子位置，这取决于return_option参数的值。如果没有找到匹配，则函数返回0。

例如：

M1	M2
7212205/7211914	20210806

目标形式

M1	M2
7212205	20210806
7211914	20210806

参考sql：

select count(*) from (
select distinct MAT_BATCH_NO,max(END_PROD_TIME) from (
select regexp_instr(MAT_BATCH_NO, '/', 1, 1) as pos, 
substr(MAT_BATCH_NO, 1-regexp_instr(MAT_BATCH_NO, '/', 1, 1)) as MAT_BATCH_NO,END_PROD_TIME
from (select distinct MAT_BATCH_NO,substr(END_PROD_TIME,0,8) AS END_PROD_TIME  from TMMSM21 T21 where MAT_BATCH_NO <> ' ')
union all 
select regexp_instr(MAT_BATCH_NO, '/', 1, 1) as pos,
substr(MAT_BATCH_NO, 0, regexp_instr(MAT_BATCH_NO, '/', 1, 1)-1) as MAT_BATCH_NO,END_PROD_TIME
from (select distinct MAT_BATCH_NO,substr(END_PROD_TIME,0,8) AS END_PROD_TIME  from TMMSM21 T21 where MAT_BATCH_NO <> ' ')
)
WHERE 1 = 1 
group by  MAT_BATCH_NO
)