问题
I understand <link-entity>
is used to do joins, but can you help me translate the following into english?
<entity name = "example">
*insert a bunch of attributes*
<link-entity name="providercertification" from="providerid" to="vendorid" alias="aa">
I understand <link-entity>
is used for joins, but the join type is not specified, so that is throwing me off. How does the link-entity work if no join type is specified? Is it automatically an inner join?
Also, which column does the from part apply to
? The very first entity or the one specified in the <link-entity
>?
Same question for the from
part.
回答1:
Per documentation the below query is totally valid, which means alias
, from
& link-type
are optional.
from
always refer to same entity as link-entity node (primary key systemuserid
of systemuser
in this case). to
refers to attribute of entity parent node (owninguser
of account
in this case)
<entity name='account'>
<attribute name='accountid'/>
<attribute name='name'/>
<link-entity name='systemuser' to='owninguser'>
Use a left outer join in FetchXML to query for records "not in"
So explicit link-type='outer'
is required for outer join
but inner join
is default.
Interestingly Fetchxml is full of surprises. You can also refer FetchXML schema
来源:https://stackoverflow.com/questions/53216249/understanding-link-entity-in-fetchxml