LEFT JOIN in Azure CosmosDB SQL API - azure

Question

I have used JOIN in Azure Cosmos DB collection using SQL API to query documents.
I have two contact documents, one is with property Address and another one is without address.
I need to get the address list of all the persons(including the persons who is not having any address). I have used the below query to do this.
But it gives the person list who is having address.
Is there any way to do LEFT JOIN?
Query:
SELECT base.FirstName, base.LastName, Address.City FROM ContactPerson
base JOIN Address IN base.Address
Sample Document:
[
{
"FirstName": "Saravana",
"LastName": "Kumar",
"Address": [
{
"City": "aaaa"
},
{
"City": "bbbb"
}
]
},
{
"FirstName": "Jayanth",
"LastName": "T"
}
]
Expected output:
[
{
"FirstName": "Saravana",
"LastName": "Kumar",
"City": "aaa"
},
{
"FirstName": "Saravana",
"LastName": "Kumar",
"City": "bbbb"
},
{
"FirstName": "Jayanth",
"LastName": "T"
}
]
Actual Output:
[
{
"FirstName": "Saravana",
"LastName": "Kumar",
"City": "bbbb"
},
{
"FirstName": "Saravana",
"LastName": "Kumar",
"City": "bbbb"
}
]

Answer 1

As i know, left join is not supported by cosmos db so far,you could vote up this thread.
As workaround,i suggest you using 2 different sql in stored procedure, then merge the results in it.
1.SELECT base.FirstName, base.LastName FROM ContactPerson base where NOT IS_DEFINED(base.Address)
2.SELECT base.FirstName, base.LastName, Address.City FROM ContactPerson base JOIN Address IN base.Address
SP:
function sample() {
var collection = getContext().getCollection();
var array = [];
var isAccepted = collection.queryDocuments(
collection.getSelfLink(),
'SELECT base.FirstName, base.LastName, Address.City FROM ContactPerson base JOIN Address IN base.Address',
function (err, feed, options) {
if (err) throw err;
if (!feed || !feed.length) {
var response = getContext().getResponse();
response.setBody('no docs found');
}
else {
array.push(feed);
}
});
var isAccepted1 = collection.queryDocuments(
collection.getSelfLink(),
'SELECT base.FirstName, base.LastName FROM ContactPerson base where NOT IS_DEFINED(base.Address)',
function (err, feed1, options) {
console.log(222)
if (err) throw err;
if (!feed1|| !feed1.length) {
var response = getContext().getResponse();
response.setBody('no docs found');
}
else {
array.push(feed1);
}
});
var response = getContext().getResponse();
response.setBody(array);
if (!isAccepted) throw new Error('The query was not accepted by the server.');
}
You could adjust the format of output as you want.

Answer 2

You can simulate LEFT JOIN with the EXISTS sentence. Eg:
SELECT VALUE c
FROM c
WHERE (
--Like a "Left Join SomeCollection"
(NOT IS_DEFINED(c.SomeCollection) OR c.SomeCollection = null)
OR EXISTS (
SELECT null
FROM s IN c.SomeCollection
WHERE s.PropertyName = 'SomeValue'
)
)
--AND/OR Some other c Node conditions

Answer 3

then don't join. you can directly access the Address field. ex:
SELECT base.FirstName, base.LastName, Address.City FROM ContactPerson base
it will just display null or empty string if it has no property