優化幫助從SQL Server

Question

查詢XML，我有以下SQL：

WITH XMLNAMESPACES ('http://schemas.tempuri.org/ef/audit/2.0' as a) 
SELECT AuditLogId, AuditDate, AuditUserId, AuditEntityActions, AuditXml 

FROM dbo.AuditLog 
WHERE 

-- user type 
(
    AuditXml.exist('/a:audit/a:entities/a:entity[a:type = "HOL.UserManagement.Data.User"]') = 1 and 
    AuditXml.exist('/a:audit/a:entities/a:entity[a:keys/a:key/a:name = "UserID"]') = 1 and 
    AuditXml.exist('/a:audit/a:entities/a:entity[a:keys/a:key/a:value = sql:variable("@userId")]') = 1 
) 

or 

-- user role type 
ISNULL(DATALENGTH(AuditXml.query(' 
    for $prop in /a:audit/a:entities/a:entity/a:properties/a:property 
    where 
    /a:audit/a:entities/a:entity[a:type = "HOL.UserManagement.Data.UserRole"] and 
    $prop[a:name = "UserId"] and 
    $prop[a:current = sql:variable("@userId")] 

    return $prop')),5) <> 5 

將從數據庫返回的任何「用戶」或「UserRole的」審覈記錄指定用戶。 「用戶」的記載很容易識別，因爲這些都是關鍵的Fileds的一部分，但是「UserRole的」記錄只能由特定的屬性（其中有很多）發現：

... 
<property> 
    <name>UserId</name> 
    <type>System.Int32</type> 
    <current xsi:type="xsd:int">2571</current> 
</property> 
... 

所以它依賴於找到屬性名稱爲UserId，當前值爲相關用戶標識。我可以簡化這個使用存在嗎？

---

使用下面的回答，我能夠把我的SQL分爲：

WITH XMLNAMESPACES ('http://schemas.tempuri.org/ef/audit/2.0' as a) 
SELECT AuditLogId, AuditDate, AuditUserId, AuditEntityActions, AuditXml 
FROM dbo.AuditLog 
WHERE 
-- user type 
(
    AuditXml.exist('/a:audit/a:entities/a:entity[a:type = "Data.User"]') = 1 and 
    AuditXml.exist('/a:audit/a:entities/a:entity[a:keys/a:key/a:name = "UserID" and a:keys/a:key/a:value = sql:variable("@UserID")]') = 1 
) 
-- user role type 
or 
(
    AuditXml.exist('/a:audit/a:entities/a:entity[a:type = "Data.UserRole"]') = 1 and 
    AuditXml.exist('/a:audit/a:entities/a:entity/a:properties/a:property[a:name/text()="UserID" and a:current/text()=sql:variable("@UserID")]') = 1 
) 

Answer 1

您可以使用XQuery謂詞結合兩個條件：

DECLARE @xml XML= 
N' 
<root xmlns:xsi="dummy"> 
<property> 
    <name>UserId</name> 
    <type>System.Int32</type> 
    <current xsi:type="xsd:int">2571</current> 
</property> 
<property> 
    <name>SomeOther</name> 
    <type>System.Int32</type> 
    <current xsi:type="xsd:int">2571</current> 
</property> 
<property> 
    <name>UserId</name> 
    <type>System.Int32</type> 
    <current xsi:type="xsd:int">1111</current> 
</property> 
<property> 
    <strangeContent/> 
</property> 
</root>'; 

DECLARE @UserId INT=2571; 
SELECT @xml.query(N'/root/property[name/text()="UserId" and current/text()=sql:variable("@UserId")]');