【场景】单据转换.选单.列表显示数量大于实际数量
【原因】一般为多个无关联实体的联查，导致的笛卡尔积
【案例】
(0)数据准备
(1)转换规则逻辑，将文本下推到下游；当且仅当另一个单据体存在整数大于10时才可推
(2)效果选单出现充分分录
【分析过程】利用APM抓执行sql
```sql
SELECT *
FROM (
SELECT t0.FBILLNO AS FBILLNO, t0.FDOCUMENTSTATUS AS FDOCUMENTSTATUS, t1.F_BHR_TEXT AS F_BHR_TEXT, t0.FID AS FID, t1.FENTRYID AS t1_FENTRYID
, ROW_NUMBER() OVER (ORDER BY t0.FID, t1.FENTRYID) AS fidentityid
FROM BHR_t_Cust100040 t0
LEFT JOIN BHR_t_Cust_Entry100227 t1 ON t0.FID = t1.FID
LEFT JOIN BHR_t_Cust_Entry100231 t3 ON t0.FID = t3.FID
WHERE t3.F_BHR_INTEGER > 10
) TLIST
WHERE fidentityid >= 1
AND fidentityid <= 200
```
因为使用了选单条件字段条件所以，会联查多一个单据体，导致单据体1的M行*单据体2的N行，笛卡尔积
【方案】调整sql条件为子查询
```sql
EXISTS (
SELECT 1 FROM BHR_t_Cust_Entry100231
WHERE BHR_t_Cust_Entry100231.FID = FID
AND BHR_t_Cust_Entry100231.F_BHR_Integer >0)
```
```sql
SELECT *
FROM (
SELECT t0.FBILLNO AS FBILLNO, t0.FDOCUMENTSTATUS AS FDOCUMENTSTATUS, t1.F_BHR_TEXT AS F_BHR_TEXT, t0.FID AS FID, t1.FENTRYID AS t1_FENTRYID
, ROW_NUMBER() OVER (ORDER BY t0.FID, t1.FENTRYID) AS fidentityid
FROM BHR_t_Cust100040 t0
LEFT JOIN BHR_t_Cust_Entry100227 t1 ON t0.FID = t1.FID
WHERE EXISTS (
SELECT 1
FROM BHR_t_Cust_Entry100231
WHERE BHR_t_Cust_Entry100231.FID = t0.FID
AND BHR_t_Cust_Entry100231.F_BHR_Integer > 10
)
) TLIST
WHERE fidentityid >= 1
AND fidentityid <= 200
```
