oracle with 语句实现递归查询

Oracle with 语句可以实现如同connect by 语句一样的序列:

connect by用法

使用rownum实现1到10的序列。

select rownum from dual connect by rownum<=10;

使用level实现1到10的序列。

select level from dual connect by level<=10;

with 可实现同样功能用法:

with c(n) as(select 1 from dualunion allselect n+1 from cwhere n<10)select n from c;

更多connect by 用法参考:https://blog.csdn.net/wang_yunj/article/details/51040029/

查询当前时间往前的12周的开始时间、结束时间、第多少周:

select sysdate - (to_number(to_char(sysdate - 1, 'd')) - 1) - (rownum - 1) * 7 as startDate, sysdate + (7 - to_number(to_char(sysdate - 1, 'd'))) - (rownum - 1) * 7 as endDate, to_number(to_char(sysdate, 'iw')) - rownum + 1 as weekIndex from dualconnect by level<= 12;--将level改成rownum可以实现同样的效果

• d 表示一星期中的第几天

• iw 表示一年中的第几周

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字符串分割，由一行变为多行:

1. 比如说分割01|02|03|04这种有规律的字符串

select REGEXP_SUBSTR('01|02|03|04', '[^|]+', 1, rownum) as newport  from dual connect by rownum <= REGEXP_COUNT('01|02|03|04', '[^|]+');