SQL ROLLUP或Union？

Question

我試圖讓條目的總計數，但不幸的是我不相信匯總會是最好的選擇：

SELECT BUSINESS_STATUS_NAME, 
    PENDING_ITEMS, 
    DATAGROUP 
FROM PAYMENTS 
WHERE STATUS LIKE '%PROCESS%'; 

這將產生：

BUSINESS_STATUS_NAME  PENDING_ITEMS  DATAGROUP 
PROCESSING DATA   34    PRODUCT 
PROCESSING INS   40    SERVICE 

我想獲得一個大總計低於，但ROLLUP給我的小計，因爲它包括數據組列。我只需要懸而未決的項目總計，但我需要顯示數據組。 UNION有總和（pending_items）選擇查詢會更好嗎？

BUSINESS_STATUS_NAME  PENDING_ITEMS  DATAGROUP 
PROCESSING DATA   34    PRODUCT 
PROCESSING INS   40    SERVICE 
GRAND TOTAL **   74 

謝謝！

Answer 1

您可以使用rollup，但你需要一個聚集查詢：

SELECT BUSINESS_STATUS_NAME, 
     SUM(PENDING_ITEMS) as PENDING_ITEMS, 
     DATAGROUP 
FROM PAYMENTS 
WHERE STATUS LIKE '%PROCESS%' 
GROUP BY ROLLUP (BUSINESS_STATUS_NAME, DATAGROUP); 

我懷疑有這樣的一個union all之間的性能差異。但是，請注意，這可保證將彙總行作爲結果集中的最後一行。

Answer 2

我會使用ROLLUP，爲了清晰和性能。

說你有一個這樣的示例表：

create table payments (business_status_name, pending_items, datagroup) as (
    select 'PROCESSING DATA', 10, 'PRODUCT' from dual union all 
    select 'PROCESSING DATA', 5, 'PRODUCT' from dual union all 
    select 'PROCESSING DATA', 2, 'SERVICE' from dual union all 
    select 'PROCESSING INS', 10, 'SERVICE' from dual union all 
    select 'PROCESSING INS', 10, 'SERVICE' from dual union all 
    select 'PROCESSING INS', 10, 'PRODUCT' from dual 
) 

這是ROLLUP的方式（注意括號來改變分組的邏輯）：

SELECT BUSINESS_STATUS_NAME, 
     SUM(PENDING_ITEMS) as PENDING_ITEMS, 
     DATAGROUP 
FROM PAYMENTS 
GROUP BY ROLLUP ((BUSINESS_STATUS_NAME, DATAGROUP)) 

結果：

BUSINESS_STATUS PENDING_ITEMS DATAGRO 
--------------- ------------- ------- 
PROCESSING INS    10 PRODUCT 
PROCESSING INS    20 SERVICE 
PROCESSING DATA   15 PRODUCT 
PROCESSING DATA    2 SERVICE 
          47 

該計劃：

--------------------------------------------------------------------------------- 
| Id | Operation   | Name  | Rows | Bytes | Cost (%CPU)| Time  | 
--------------------------------------------------------------------------------- 
| 0 | SELECT STATEMENT  |   |  6 | 186 |  4 (25)| 00:00:01 | 
| 1 | SORT GROUP BY ROLLUP|   |  6 | 186 |  4 (25)| 00:00:01 | 
| 2 | TABLE ACCESS FULL | PAYMENTS |  6 | 186 |  3 (0)| 00:00:01 | 
--------------------------------------------------------------------------------- 

這是UNION ALL：

SELECT BUSINESS_STATUS_NAME, 
     SUM(PENDING_ITEMS) as PENDING_ITEMS, 
     DATAGROUP 
FROM PAYMENTS 
GROUP BY BUSINESS_STATUS_NAME, DATAGROUP 
UNION ALL 
SELECT NULL, SUM(PENDING_ITEMS), NULL 
FROM PAYMENTS; 

結果比ROLLUP相同：

BUSINESS_STATUS PENDING_ITEMS DATAGRO 
--------------- ------------- ------- 
PROCESSING INS    20 SERVICE 
PROCESSING INS    10 PRODUCT 
PROCESSING DATA   15 PRODUCT 
PROCESSING DATA    2 SERVICE 
          47 

的計劃也不是那麼好，TWO FULL SCANS：

-------------------------------------------------------------------------------- 
| Id | Operation   | Name  | Rows | Bytes | Cost (%CPU)| Time  | 
-------------------------------------------------------------------------------- 
| 0 | SELECT STATEMENT |   |  7 | 199 |  7 (58)| 00:00:01 | 
| 1 | UNION-ALL   |   |  |  |   |   | 
| 2 | HASH GROUP BY  |   |  6 | 186 |  4 (25)| 00:00:01 | 
| 3 | TABLE ACCESS FULL| PAYMENTS |  6 | 186 |  3 (0)| 00:00:01 | 
| 4 | SORT AGGREGATE |   |  1 | 13 |   |   | 
| 5 | TABLE ACCESS FULL| PAYMENTS |  6 | 78 |  3 (0)| 00:00:01 | 
-------------------------------------------------------------------------------- 

這當然只有一個有少量記錄的小示例，沒有索引，......因此，真實表格上的內容可能會有所不同，但我仍然認爲ROLLUP應該比UNION ALL更好。

在一個簡單的情況下，完全等於你的，這將是這兩種方法的計劃：

SELECT BUSINESS_STATUS_NAME, 
     SUM(PENDING_ITEMS) as PENDING_ITEMS, 
     DATAGROUP 
FROM PAYMENTS 
GROUP BY ROLLUP ((BUSINESS_STATUS_NAME, DATAGROUP)) 

--------------------------------------------------------------------------------- 
| Id | Operation   | Name  | Rows | Bytes | Cost (%CPU)| Time  | 
--------------------------------------------------------------------------------- 
| 0 | SELECT STATEMENT  |   |  2 | 62 |  4 (25)| 00:00:01 | 
| 1 | SORT GROUP BY ROLLUP|   |  2 | 62 |  4 (25)| 00:00:01 | 
| 2 | TABLE ACCESS FULL | PAYMENTS |  2 | 62 |  3 (0)| 00:00:01 | 
--------------------------------------------------------------------------------- 

SELECT BUSINESS_STATUS_NAME, 
     PENDING_ITEMS, 
     DATAGROUP 
FROM PAYMENTS 
UNION ALL 
SELECT NULL, 
     SUM(PENDING_ITEMS), 
     NULL 
FROM PAYMENTS  

-------------------------------------------------------------------------------- 
| Id | Operation   | Name  | Rows | Bytes | Cost (%CPU)| Time  | 
-------------------------------------------------------------------------------- 
| 0 | SELECT STATEMENT |   |  3 | 75 |  6 (50)| 00:00:01 | 
| 1 | UNION-ALL   |   |  |  |   |   | 
| 2 | TABLE ACCESS FULL | PAYMENTS |  2 | 62 |  3 (0)| 00:00:01 | 
| 3 | SORT AGGREGATE |   |  1 | 13 |   |   | 
| 4 | TABLE ACCESS FULL| PAYMENTS |  2 | 26 |  3 (0)| 00:00:01 | 
-------------------------------------------------------------------------------- 

ROLLUP仍然有一個表掃描一個更好的計劃。