条件连接性能优化 - Oracle SQL

Question

我需要查看我们数据库中的一个实物，它可以是我的小型建筑公司处理的任何类型的交易。然后，根据交易类型，确定到期日期和承诺日期。有十五种不同的交易类型，但我主要关注四五种：

SELECT
    datatable.ID_Number,
    datatable.Object_Type,
    CASE
        WHEN Object_Type = 'AA' THEN (SELECT PO_DUE_DATE FROM tblPO WHERE datatable.ID_Number = tblPO.PO_ID)
        WHEN Object_Type = 'AB' THEN (SELECT PROD_DUE_DATE FROM tblPROD WHERE datatable.ID_Number = tblPROD.PROD_ID)
        WHEN Object_Type = 'AC' THEN (SELECT PLAN_DUE_DATE FROM tblPLAN WHERE datatable.ID_Number = tblPLAN.PLAN_ID)
        WHEN Object_Type = 'BN' THEN (SELECT NEED_DUE_DATE FROM tblPURCHASE WHERE datatable.ID_Number = tblPURCHASE.PURCHASE_ID)
    ELSE TO_DATE(NULL) END AS Object_Due_Date,
    CASE
        WHEN Object_Type = 'AA' THEN (SELECT PO_PROM_DATE FROM tblPO WHERE datatable.ID_Number = tblPO.PO_ID)
        WHEN Object_Type = 'AB' THEN (SELECT PROD_PROM_DATE FROM tblPROD WHERE datatable.ID_Number = tblPROD.PROD_ID)
        WHEN Object_Type = 'AC' THEN (SELECT PLAN_PROM_DATE FROM tblPLAN WHERE datatable.ID_Number = tblPLAN.PLAN_ID)
        WHEN Object_Type = 'BN' THEN (SELECT NEED_PROM_DATE FROM tblPURCHASE WHERE datatable.ID_Number = tblPURCHASE.PURCHASE_ID)
    ELSE TO_DATE(NULL) END AS Object_Promised_Date

FROM
    datatable

WHERE
    ( other filtering criteria )

这给了我这样的输出：

| ID_Number | Object_Type | Object_Due_Date | Object_Promised_Date |
|:---------:|:-----------:|:---------------:|:--------------------:|
|     1     |      AA     |    11/26/2018   |      10/18/2018      |
|     2     |      AB     |    5/12/2018    |       3/31/2018      |
|     3     |      AA     |    6/15/2018    |       9/18/2018      |
|     4     |      AA     |    1/24/2018    |       10/2/2018      |
|     5     |      ZZ     |    10/27/2018   |       6/11/2018      |
|     7     |      BN     |    1/23/2018    |       7/2/2018       |
|     8     |      AC     |     4/3/2018    |       8/3/2018       |
|     9     |      BN     |    12/1/2018    |       8/16/2018      |
|     10    |      BN     |    1/10/2018    |       10/6/2018      |

而且效果很好！问题是datatable 大约有 2000 万条记录，而且这些日期可能会发生变化，因此我需要每隔一段时间（每周一次或两次）刷新报告。运行和更新需要 8-9 小时，因为对于每条记录，我都会有条件地加入另一个表。

如何提高此查询的运行时效率？我知道我可以离开表格加入，但我不知道如何用日期填充单个列值，具体取决于Object_Type，而不是为Type_AA_Due_DateType_AB_ Due_Date 等设置 n 列。

Answer 1

你也可以试试这个方法：

SELECT
    datatable.ID_Number,
    datatable.Object_Type,
    COALESCE (tblPO.PO_DUE_DATE, tblPROD.PROD_DUE_DATE, tblPLAN.PLAN_DUE_DATE, 
              tblPURCHASE.NEED_DUE_DATE) AS Object_Due_Date,
    COALESCE (tblPO.PO_PROM_DATE, tblPROD.PROD_PROM_DATE, tblPLAN.PLAN_PROM_DATE,
              NEED_PROM_DATE.NEED_DUE_DATE) AS Object_Promised_Date
FROM
    datatable
    LEFT JOIN tblPO 
       ON  datatable.ID_Number = tblPO.PO_ID
       AND datatable.Object_Type = 'AA'
    LEFT JOIN tblPROD 
       ON  datatable.ID_Number = tblPROD.PROD_ID
       AND datatable.Object_Type = 'AB'
    LEFT JOIN tblPLAN 
       ON  datatable.ID_Number = tblPLAN.PLAN_ID
       AND datatable.Object_Type = 'AC'
    LEFT JOIN tblPURCHASE
       ON  datatable.ID_Number = tblPURCHASE.PURCHASE_ID
       AND datatable.Object_Type = 'BN'
WHERE
    ( other filtering criteria )

Answer 2

试试这个

SELECT
    datatable.ID_Number,
    datatable.Object_Type,
    tblPO.PO_DUE_DATE Object_Due_Date,
    tblPO.PO_PROM_DATE Object_Promised_Date
FROM
    datatable
join tblPO on  datatable.ID_Number = tblPO.PO_ID
WHERE
  Object_Type = 'AA' 
    ( other filtering criteria )

union all

SELECT
    datatable.ID_Number,
    datatable.Object_Type,
    tblPROD.PROD_DUE_DATE, 
    tblPROD.PROD_PROM_DATE 
FROM
    datatable
join tblPLAN on  datatable.ID_Number = tblPLAN.PLAN_ID
WHERE
  Object_Type = 'AB' 
    ( other filtering criteria )

union all 

as early with tables tblPLAN and  tblPURCHASE 

Answer 3

这样的事情怎么样？

SELECT
  dt.ID_Number,
  dt.Object_Type,
  CASE
    WHEN Object_Type = 'AA' THEN po.PO_DUE_DATE
    WHEN Object_Type = 'AB' THEN pd.PROD_DUE_DATE
    WHEN Object_Type = 'AC' THEN pl.PLAN_DUE_DATE
    WHEN Object_Type = 'BN' THEN pc.NEED_DUE_DATE
  ELSE TO_DATE(NULL) END AS Object_Due_Date,
  CASE
    WHEN Object_Type = 'AA' THEN po.PO_PROM_DATE
    WHEN Object_Type = 'AB' THEN pd.PROD_PROM_DATE
    WHEN Object_Type = 'AC' THEN pl.PLAN_PROM_DATE
    WHEN Object_Type = 'BN' THEN pc.NEED_PROM_DATE
  ELSE TO_DATE(NULL) END AS Object_Promised_Date
FROM
  datatable dt
LEFT JOIN tblPO po ON dt.ID_Number = po.PO_ID
LEFT JOIN tblPROD pd ON dt.ID_Number = pd.PROD_ID
LEFT JOIN tbdPLAN pl ON dt.ID_Number = pl.PLAN_ID
LEFT JOIN tblPURCHASE pc ON dt.ID_Number = pc.PURCHASE_ID
WHERE
    ( other filtering criteria )

我刚刚将您的条件 SELECTs 替换为 LEFT JOINs。您可以在此查询与您的原始查询上运行EXPLAIN PLAN，看看是否有任何改变。

其他想法

• 如果您还没有在datatable.ID_Number 上定义索引，那么您应该在其上创建一个索引，因为它可以在所有SELECTs / JOINs 中访问

• 如果您的其他 JOIN 列（PO_ID、PROD_ID、...）尚未编入索引，则可能在它们上创建索引

• 如果您知道行将始终存在于 LEFT JOIN 表中，请将连接更改为 INNER JOIN...这可能会加快速度

Answer 4

类似于 Needle 的回答，但我喜欢将来自不同来源的相似数据组合到一个视图中。在这种情况下，我使用的是内联视图，但如果您要在很多地方使用它，那么创建一个实际视图以显示不同交易类型的到期日期和承诺日期可能是值得的。

SELECT
    datatable.ID_Number,
    datatable.Object_Type,
    type_lookups.Object_Due_Date,
    type_lookups.Object_Promised_Date
FROM
    datatable
LEFT JOIN (
    select 'AA' as Object_Type,
        PO_DUE_DATE as Object_Due_Date,
        PO_PROM_DATE as Object_Promised_Date,
        PO_ID as ID
    from tblPO
    union all
    select 'AB' as Object_Type,
        PROD_DUE_DATE as Object_Due_Date,
        PROD_PROM_DATE as Object_Promised_Date,
        PROD_ID as ID
    from tblPROD 
    union all
    select 'AC' as Object_Type,
        PLAN_DUE_DATE as Object_Due_Date,
        PLAN_PROM_DATE as Object_Promised_Date,
        PLAN_ID as ID
    from tblPLAN
    union all
    select 'BN' as Object_Type,
        NEED_DUE_DATE as Object_Due_Date,
        NEED_PROM_DATE as Object_Promised_Date,
        PURCHASE_ID as ID
    from tblPURCHASE
    ) type_lookups
  ON type_lookups.object_type = datatable.Object_Type
  AND type_lookups.ID = datatable.ID_Number
WHERE
    ( other filtering criteria )