# 案例：With-Recursive contains system table is not shippable
#### 问题根因
递归语句的某个分支中没有完整的From子句，仅使用系统表或者系统视图(DUAL也被视为系统视图)代替。
#### 案例1：递归驱动分支是FROM DUAL查询
**原始语句**
```
WITH recursive cte AS (
    SELECT 
        TO_DATE(201701, 'YYYYMM') as level ,TO_DATE(20170131, 'YYYYMMDD')  LASTDAY  
    FROM dual 
    UNION ALL 
    SELECT
        ADD_MONTHS(cte.LEVEL,   1) AS PERIOD,
        LAST_DAY(ADD_MONTHS(cte.LEVEL,   1)) AS LASTDAY
    FROM cte WHERE cte.LEVEL <=SYSDATE 
) 
SELECT 
    TO_CHAR(cte.level,'YYYYMMDD') AS PERIOD , cte.LASTDAY 
    FROM cte
WHERE TO_CHAR(cte.level,'YYYYMMDD')<= TO_CHAR(SYSDATE,'YYYYMMDD')
```
**改写语句**
```
WITH recursive cte AS (
    SELECT 
        TO_DATE(201701, 'YYYYMM') as level ,TO_DATE(20170131, 'YYYYMMDD')  LASTDAY  
    FROM generate_series(1, 1) 
    UNION ALL 
    SELECT
        ADD_MONTHS(cte.LEVEL,   1) AS PERIOD,
        LAST_DAY(ADD_MONTHS(cte.LEVEL,   1)) AS LASTDAY
    FROM cte WHERE cte.LEVEL <=SYSDATE 
) 
SELECT 
    TO_CHAR(cte.level,'YYYYMMDD') AS PERIOD , cte.LASTDAY 
    FROM cte
WHERE TO_CHAR(cte.level,'YYYYMMDD')<= TO_CHAR(SYSDATE,'YYYYMMDD')
```
**修改点对比**
![](https://support.huaweicloud.com/devg-dws/figure/zh-cn_image_0000002525801453.png "点击放大")