How to query nested array with Cosmos DB - azure-cosmosdb

Question

Given the following JSON
{
"Families": [
{ "Name": "Smith",
"Children": [
{ "Name": "Bob",
"Pets": [
{ "Name": "Oscar", "Type": "Cat"},
{ "Name": "Otto", "Type": "Dog"}
]
},
{ "Name": "Brittney",
"Pets": [
{ "Name": "Isolde", "Type": "Dog"},
{ "Name": "Ignatz", "Type": "Turtle"}
]
}
]
},
{ "Name": "Miller",
"Children": [
{ "Name": "Alex",
"Pets": [
{ "Name": "Elvis", "Type": "Horse"}
]
}
]
}
]
}
A) I'd like to create a query that yields the following structure
[
{ "FamilyName": "Smith",
"KidName": "Bob",
"Petname": "Oscar"
},
{ "FamilyName": "Smith",
"KidName": "Bob",
"Petname": "Otto"
},
{ "FamilyName": "Smith",
"KidName": "Brittney",
"Petname": "Isolde"
},
{ "FamilyName": "Smith",
"KidName": "Brittney",
"Petname": "Ignatz"
},
{ "FamilyName": "Miller",
"KidName": "Alex",
"Petname": "Elvis"
}
]
B) I'd like to create a query that yields this slightly different structure
[
{ "FamilyName": "Smith",
"KidName": "Bob",
"Petnames": ["Oscar", Otto"]
},
{ "FamilyName": "Smith",
"KidName": "Brittney",
"Petname": ["Isolde", "Ignatz"]
},
{ "FamilyName": "Miller",
"KidName": "Alex",
"Petname": ["Elvis"]
}
]
Your help is greatly appreciated
Robert

Answer 1

There is actually a really good doc for this here: https://learn.microsoft.com/en-us/azure/cosmos-db/sql-query-join and here: https://learn.microsoft.com/en-us/azure/cosmos-db/sql-query-object-array#arrays
For arrays, you want to utilize nested joins, like so:
Given:
{
"id": "so-test",
"Families": [
{
"Name": "Smith",
"Children": [
{
"Name": "Bob",
"Pets": [
{
"Name": "Oscar",
"Type": "Cat"
},
{
"Name": "Otto",
"Type": "Dog"
}
]
},
{
"Name": "Brittney",
"Pets": [
{
"Name": "Isolde",
"Type": "Dog"
},
{
"Name": "Ignatz",
"Type": "Turtle"
}
]
}
]
},
{
"Name": "Miller",
"Children": [
{
"Name": "Alex",
"Pets": [
{
"Name": "Elvis",
"Type": "Horse"
}
]
}
]
}
]
}
You can use this query for A:
SELECT
f.Name as FamilyName,
c.Name as KidName,
p.Name as Petname
FROM d
JOIN f IN d.Families
JOIN c IN f.Children
JOIN p IN c.Pets
WHERE d.id = "so-test"
and you'll get this result:
[
{
"FamilyName": "Smith",
"KidName": "Bob",
"Petname": "Oscar"
},
{
"FamilyName": "Smith",
"KidName": "Bob",
"Petname": "Otto"
},
{
"FamilyName": "Smith",
"KidName": "Brittney",
"Petname": "Isolde"
},
{
"FamilyName": "Smith",
"KidName": "Brittney",
"Petname": "Ignatz"
},
{
"FamilyName": "Miller",
"KidName": "Alex",
"Petname": "Elvis"
}
]
For B), use this query which adds the ARRAY method
SELECT
f.Name as FamilyName,
c.Name as KidName,
ARRAY(SELECT DISTINCT VALUE p.Name from p IN c.Pets) as Petname
FROM d
JOIN f IN d.Families
JOIN c IN f.Children
WHERE d.id = "so-test"
you'll get these results:
[
{
"FamilyName": "Smith",
"KidName": "Bob",
"Petname": [
"Oscar",
"Otto"
]
},
{
"FamilyName": "Smith",
"KidName": "Brittney",
"Petname": [
"Isolde",
"Ignatz"
]
},
{
"FamilyName": "Miller",
"KidName": "Alex",
"Petname": [
"Elvis"
]
}
]