Question

QUERY 1

WITH CUST1 AS
(SELECT CUSTOMER_ID, TYPE FROM CUSTOMERS WHERE CONDITION),
    CARS1 AS
(SELECT * FROM CARS INNER JOIN CUST1 ON
    CUST1.CUSTOMER_ID = CARS.CUSTOMER_ID AND
    CUST1.TYPE = CARS.TYPE) select * from CARS1;

CUSTOMERE TABLE

    CUSTOMER_ID ||    TYPE        
    ------------||  -------       
    1           ||     5          
    2           ||     5          
    3           ||     2          
    4           ||     2

CARS TABLE

CAR_ID  ||  CUSTOMER_ID  ||   TYPE   ||   SN   ||  DATE                                      
------- ||  ------------ ||   ------ ||  ----- || -------
1       ||  1            ||    5     ||  0123  ||  02/06/1999
2       ||  1            ||    2     ||  2365  ||  03/08/1999             
3       ||  1            ||    3     ||  5156  ||  03/02/1999       
4       ||  3            ||    1     ||  8651  ||  03/03/1999       
5       ||  2            ||    5     ||  2555  ||  03/09/1999       
6       ||  2            ||    2     ||  8562  ||  03/18/1999

QUERY 1结果

CAR_ID  ||  CUSTOMER_ID  ||   TYPE   || SN    ||  DATE      
------- ||  ------------ ||  ------  || ----- || --------  
1       ||    1          ||     5    || 0123  || 02/06/1999
5       ||    2          ||     5    || 2555  || 03/09/1999

以上查询加入临时表＆＃34; CUST1＆＃34;用实际表格＆＃34; CARS＆＃34;列CUSTOMER_ID和TYPE上。现在，我希望实现的是从CARS中选择属于客户的DATE AS DATE2和SN AS SN2 对于CUSTOMER_ID，CARS.TYPE = 2来自JOIN条件。

然而，困境在于我不想重新加入/使用子查询，因为CARS表非常大。由于其他原因，请忽略临时表方法，因为它在其余代码中使用。当前列为CUSTOMER_ID，基于CUSTOMER_ID的其他两列为SN和TYPE。

预期结果

CAR_ID  ||   CUSTOMER_ID  ||   TYPE  || SN    ||  DATE      || DATE2       ||  SN2
------- ||   ------------ ||  ------ || ----- || --------   || -------     || -----
1       ||      1         ||     5   || 0123  || 02/06/1999 || 03/08/1999  ||  2365
5       ||      2         ||     5   || 2555  || 03/09/1999 || 03/18/1999  ||  8562

Answer 1

我认为条件聚合会做你想要的。我不确定实际的逻辑是什么，但它似乎是沿着这些方向：

SELECT CAR_ID, CUSTOMER_ID, 5 as TYPE,
       MAX(CASE WHEN TYPE = 5 THEN SN END) as SN,
       MAX(CASE WHEN TYPE = 5 THEN DATE END) as DATE,
       MAX(CASE WHEN TYPE = 2 THEN SN END) as SN2,
       MAX(CASE WHEN TYPE = 2 THEN DATE END) as DATE2,
 CARS c INNER JOIN CUST1 cu
     ON cu.CUSTOMER_ID = c.CUSTOMER_ID AND
        cu.TYPE = c.TYPE
WHERE CONDITION
GROUP BY CAR_ID, CUSTOMER_ID;

Answer 2

我不确定你可以不加入汽车。你的汽车桌有多大？使用我的简单测试，我发现我正在创建一个布隆过滤器，它可能足以使查询执行。为什么不尝试看看你是否真的有问题？也许发布执行计划。例如：

 select c.car_id, c.customer_id, c.type, c.sn, c.car_date, c2.sn, c2.car_date, c2.sn 
from cars c 
join cust cu 
on c.customer_id = cu.customer_id 
and c.type = cu.type 
join cars c2 
on c2.customer_id = cu.customer_id 
where c2.type = 2

给出

    CAR_ID CUSTOMER_ID       TYPE SN   CAR_DATE  SN   CAR_DATE  SN
---------- ----------- ---------- ---- --------- ---- --------- ----
         1           1          5 0123 06-FEB-99 2365 08-MAR-99 2365
         5           2          5 2555 09-MAR-99 8652 18-MAR-99 8652

select * from table( dbms_xplan.display_cursor( null, null, 'TYPICAL' ) );

----------------------------------------------------------------
| Id  | Operation                    | Name    | Rows  | Bytes |
----------------------------------------------------------------
|   0 | SELECT STATEMENT             |         |       |       |
|*  1 |  HASH JOIN                   |         |     2 |   234 |
|   2 |   JOIN FILTER CREATE         | :BF0000 |     2 |   130 |
|*  3 |    HASH JOIN                 |         |     2 |   130 |
|*  4 |     TABLE ACCESS STORAGE FULL| CARS    |     2 |    78 |
|   5 |     TABLE ACCESS STORAGE FULL| CUST    |     4 |   104 |
|   6 |   JOIN FILTER USE            | :BF0000 |     6 |   312 |
|*  7 |    TABLE ACCESS STORAGE FULL | CARS    |     6 |   312 |
----------------------------------------------------------------

根据所选的当前列选择列（SQL）

2 个答案: