Click here to Skip to main content
Click here to Skip to main content

Difference between CROSS APPLY and OUTER APPLY of SQL XML

, 19 Jul 2012
Rate this:
Please Sign up or sign in to vote.
The difference between CROSS APPLY and OUTER APPLY of SQL XML

Introduction

The APPLY operator comes in two variants, CROSS APPLY and OUTER APPLY. It is useful for joining two SQL tables or XML expressions. CROSS APPLY is equivalent to an INNER JOIN expression and OUTER APPLY is equivalent to a LEFT OUTER JOIN expression.

Solution

Sample XML

DECLARE @XML XML = 
<span class="str">'<Root>
    <UserInfo Id="1" Name="Name 1">
        <CityInfo Id="2" City="City 1" />
        <CityInfo Id="3" City="City 2" >
            <PrefInfo Id="33" Name="Show Whether" />
        </CityInfo>
    </UserInfo>
    <UserInfo Id="2" Name="Name 2">
        <CityInfo Id="4" City="City 3" />
        <CityInfo Id="5" City="City 4" >
            <PrefInfo Id="33" Name="Show Temprature" />
        </CityInfo>
    </UserInfo>
</Root>'</span>

Cross Apply

Cross apply basically uses inner join of two XML collections

SELECT
    UserInfo.value('@Id', 'BIGINT') as UserId
    , UserInfo.value('@Name', 'VARCHAR(20)') as UserName
    , CityInfo.value('@Id', 'BIGINT') as CityId
    , CityInfo.value('@City', 'VARCHAR(20)') as CityName
    , PrefInfo.value('@Id', 'BIGINT') as PrefId
    , PrefInfo.value('@Name', 'VARCHAR(20)') as PrefName
FROM @xml.nodes('/Root/UserInfo')e(UserInfo)
    CROSS APPLY UserInfo.nodes('CityInfo')b(CityInfo)
    CROSS APPLY CityInfo.nodes('PrefInfo')c(PrefInfo)

Output

UserId   UserName  CityId  CityName  PrefId   PrefName
-------- --------- ------- --------- -------- ----------------
1        Name 1    3       City 2    33       Show Whether
2        Name 2    5       City 4    33       Show Temprature 

Outer Apply

Outer apply basically uses left outer join of two XML collections

SELECT
    UserInfo.value('@Id', 'BIGINT') as UserId
    , UserInfo.value('@Name', 'VARCHAR(20)') as UserName
    , CityInfo.value('@Id', 'BIGINT') as CityId
    , CityInfo.value('@City', 'VARCHAR(20)') as CityName
    , PrefInfo.value('@Id', 'BIGINT') as PrefId
    , PrefInfo.value('@Name', 'VARCHAR(20)') as PrefName
FROM @xml.nodes('/Root/UserInfo')e(UserInfo)
    CROSS APPLY UserInfo.nodes('CityInfo')b(CityInfo)
    OUTER APPLY CityInfo.nodes('PrefInfo')c(PrefInfo)

Output

UserId  UserName  CityId  CityName  PrefId  PrefName
------- --------- ------- --------- ------- ----------------
1       Name 1    2       City 1    NULL    NULL
1       Name 1    3       City 2    33      Show Whether
2       Name 2    4       City 3    NULL    NULL
2       Name 2    5       City 4    33      Show Temprature 

Originally posted @ JSD Ideas[^]

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

jsd24
Technical Lead
India India
No Biography provided

Comments and Discussions

 
GeneralNot Enough Content [modified] PinmemberTim Corey16-Jul-12 1:37 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Mobile
Web03 | 2.8.140821.2 | Last Updated 19 Jul 2012
Article Copyright 2012 by jsd24
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid