MSSQL：以下代码的替代方法，这花费太多时间才能获得结果

问题描述

我想知道如何简单地编写下面的代码，并且我有兴趣避免代码重复。还有其他方法吗？是

1. 无论[invoices_global]表中的字段发生什么变化，这些更改都将以old_value，new_value，field_changed的格式作为新记录插入到Change log表中。

2. 单个字段可能会被许多用户更新，因此应该使用最新的字段，这就是为什么我在代码中提到了last_updated_datetime desc的原因。

3. 需要避免重复。

4. 性能改进，因为我一次又一次针对单个ap_work_id调用同一张表。提取结果需要18秒-40000中的2000。

5. FYI，system_id和ap_work_id相同。

        SELECT
            api.ap_work_id,api.invoice_status,api.po_number,api.po_value,api.region,api.invoice_value,api.invoice_value_currency,em3.employee_full_name AS invoice_owner,(
                **SELECT TOP 1
                    old_value
                FROM    change_log cl
                WHERE  field_changed = 'ARIBA INVOICE ID' AND api.ap_work_id = cl.
                system_id AND system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS bot_ariba_id_value,(
                **SELECT TOP 1
                    new_value
                FROM   change_log cl
                WHERE  field_changed = 'ARIBA INVOICE ID' AND api.ap_work_id = cl.
                system_id AND cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS processor_ariba_id_value,(
                **SELECT TOP 1
                    old_value
                FROM   change_log cl
                WHERE  field_changed = 'PO NUMBER' AND api.ap_work_id = cl.system_id AND
                cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS bot_po_number,(
                **SELECT TOP 1
                    new_value
                FROM   change_log cl
                WHERE  field_changed = 'PO NUMBER' AND api.ap_work_id = cl.system_id AND
                cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS processor_po_number,(
                **SELECT TOP 1
                    old_value
                FROM   change_log cl
                WHERE  field_changed = 'vendOR NAME' AND api.ap_work_id = cl.system_id
                AND cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS bot_vendor_name,(
                **SELECT TOP 1
                    new_value
                FROM   change_log cl
                WHERE  field_changed = 'vendOR NAME' AND api.ap_work_id = cl.system_id
                AND cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS processor_vendor_name,(
                **SELECT TOP 1
                    old_value
                FROM   change_log cl
                WHERE  field_changed = 'INVOICE VALUE' AND api.ap_work_id = cl.system_id
                AND cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS bot_invoice_value,(
                **SELECT TOP 1
                    new_value
                FROM   change_log cl
                WHERE  field_changed = 'INVOICE VALUE' AND api.ap_work_id = cl.system_id
                AND cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS processor_invoice_value,(
                **SELECT TOP 1
                    old_value
                FROM   change_log cl
                WHERE  field_changed = 'INVOICE CURRENCY' AND api.ap_work_id = cl.
                system_id AND cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS bot_invoice_currency,(
                **SELECT TOP 1
                    new_value
                FROM   change_log cl
                WHERE  field_changed = 'INVOICE CURRENCY' AND api.ap_work_id = cl.
                system_id AND cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS processor_invoice_currency,(
                **SELECT TOP 1
                    old_value
                FROM   change_log cl
                WHERE  field_changed = 'INVOICE DATE' AND api.ap_work_id = cl.system_id
                AND cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS bot_invoice_date,(
                **SELECT TOP 1
                    new_value
                FROM   change_log cl
                WHERE  field_changed = 'INVOICE DATE' AND api.ap_work_id = cl.system_id
                AND cl.system_type = 'INVOICE'
                ORDER BY
                        last_updated_datetime DESC**
            ) AS processor_invoice_date
    FROM invoices_global api
        OUTER APPLY
    (
        SELECT TOP 1
            *
        FROM   transactions t
        WHERE  t.po_number = api.po_number AND t.po_number <> ''
        ORDER BY
                t.last_updated_datetime DESC
    ) AS t
        LEFT JOIN employee_master em3
        ON em3.ldap = api.invoice_owner_ldap
        LEFT JOIN vendor v
        ON v.vendor_number = api.vendor_number
        LEFT JOIN cost_center cc
        ON cc.cost_ctr = api.cost_center
    WHERE DATEDIFF(DAY,api.approved_date,GETDATE()) <= 30
    GROUP BY
            api.ap_work_id,api.category,em3.employee_full_name,api.invoice_date,api.due_date,api.company_code,api.vendor_number,t.company_code,api.cost_center,v.vendor_name,v.vendor_number,cc.company;
   

解决方法

这是您的一种方法

• 为system_id和field_changed的每种组合创建具有最新值的派生表
• 将派生表联接到原始api表，并将值放入各个字段

当前使用MAX（CASE（）），但您可以将其作为PIVOT。

此处仅包含SQL的顶部（与问题相关）-您需要在底部进行其他联接。我还没有测试过（没有表结构等），所以我不能保证没有错字。

; WITH LatestCL AS
        (SELECT * 
            FROM    (SELECT system_id AS ap_work_id,field_changed,old_value,new_value,ROW_NUMBER () OVER (PARTITION BY system_id,field_changed ORDER BY last_updated_datetime DESC) AS rn
                    FROM change_log
                    WHERE system_type = 'INVOICE'
                    ) cl
            WHERE cl.rn = 1
        )
SELECT  api.ap_work_id,api.invoice_status,api.po_number,api.po_value,api.region,api.invoice_value,api.invoice_value_currency,MAX(CASE WHEN field_changed = 'ARIBA INVOICE ID' THEN old_value ELSE NULL END) AS bot_ariba_id_value,MAX(CASE WHEN field_changed = 'ARIBA INVOICE ID' THEN new_value ELSE NULL END) AS processor_ariba_id_value,MAX(CASE WHEN field_changed = 'PO NUMBER' THEN old_value ELSE NULL END) AS bot_po_number,MAX(CASE WHEN field_changed = 'PO NUMBER' THEN new_value ELSE NULL END) AS processor_po_number,MAX(CASE WHEN field_changed = 'VENDOR NAME' THEN old_value ELSE NULL END) AS bot_vendor_name,MAX(CASE WHEN field_changed = 'VENDOR NAME' THEN new_value ELSE NULL END) AS processor_vendor_name,MAX(CASE WHEN field_changed = 'INVOICE VALUE' THEN old_value ELSE NULL END) AS bot_invoice_value,MAX(CASE WHEN field_changed = 'INVOICE VALUE' THEN new_value ELSE NULL END) AS processor_invoice_value,MAX(CASE WHEN field_changed = 'INVOICE CURRENCY' THEN old_value ELSE NULL END) AS bot_invoice_currency,MAX(CASE WHEN field_changed = 'INVOICE CURRENCY' THEN new_value ELSE NULL END) AS processor_invoice_currency,MAX(CASE WHEN field_changed = 'INVOICE DATE' THEN old_value ELSE NULL END) AS bot_invoice_date,MAX(CASE WHEN field_changed = 'INVOICE DATE' THEN new_value ELSE NULL END) AS processor_invoice_date
FROM    invoices_global api
        INNER JOIN LatestCL ON api.ap_work_id = LatestCL.ap_work_id