Flatten JSON Data on snowflake - snowflake-cloud-data-platform

Question

below is the Json data I'm trying to Flatten on snowflake
Json Document :
[
"empDetails": [
{
"kind": "person",
"fullName": "John Doe",
"age": 22,
"gender": "Male",
"phoneNumber": {
"areaCode": "206",
"number": "1234567"
},
"children": [
{
"name": "Jane",
"gender": "Female",
"age": "6"
},
{
"name": "John",
"gender": "Male",
"age": "15"
}
],
"citiesLived": [
{
"place": "Seattle",
"yearsLived": [
"1995"
]
},
{
"place": "Stockholm",
"yearsLived": [
"2005"
]
}
]
},
{
"kind": "person",
"fullName": "Mike Jones",
"age": 35,
"gender": "Male",
"phoneNumber": {
"areaCode": "622",
"number": "1567845"
},
"children": [
{
"name": "Earl",
"gender": "Male",
"age": "10"
},
{
"name": "Sam",
"gender": "Male",
"age": "6"
},
{
"name": "Kit",
"gender": "Male",
"age": "8"
}
],
"citiesLived": [
{
"place": "Los Angeles",
"yearsLived": [
"1989",
"1993",
"1998",
"2002"
]
},
{
"place": "Washington DC",
"yearsLived": [
"1990",
"1993",
"1998",
"2008"
]
},
{
"place": "Portland",
"yearsLived": [
"1993",
"1998",
"2003",
"2005"
]
},
{
"place": "Austin",
"yearsLived": [
"1973",
"1998",
"2001",
"2005"
]
}
]
},
{
"kind": "person",
"fullName": "Anna Karenina",
"age": 45,
"gender": "Female",
"phoneNumber": {
"areaCode": "425",
"number": "1984783"
},
"citiesLived": [
{
"place": "Stockholm",
"yearsLived": [
"1992",
"1998",
"2000",
"2010"
]
},
{
"place": "Russia",
"yearsLived": [
"1998",
"2001",
""
]
},
{
"place": "Austin",
"yearsLived": [
"1995",
"1999"
]
}
]
}
]
}
In this data I have 3 employees and their details like Name, children, cities Lived
but for one of the employee "Anna Karenina" children details are not there, but for other 2 employees have children data.
because of the missing children details I'm not able to flatten 3rd emp data.
below is what I have tried so far :
Snowflake Flatten Json Code :
select empd.value:kind,
empd.value:fullName,
empd.value:age,
empd.value:gender,
--empd.value:phoneNumber,
empd.value:phoneNumber.areaCode,
empd.value:phoneNumber.number ,
empd.value:children -- flattening childrean
//chldrn.value:name,
//chldrn.value:gender,
//chldrn.value:age,
//city.value:place,
//yr.value:yearsLived
from my_json emp , lateral flatten(input=>emp.Json_data:empDetails) empd ,
lateral flatten(input=>empd.value:children) chldrn,
//lateral flatten(input=>empd.value:citiesLived) city,
//lateral flatten(input=>city.value:yearsLived) yr

Answer 1

You need to use OUTER switch:
FLATTEN
OUTER => TRUE | FALSE
If FALSE, any input rows that cannot be expanded, either because they cannot be accessed in the path or because they have zero fields or entries, are completely omitted from the output.
If TRUE, exactly one row is generated for zero-row expansions (with NULL in the KEY, INDEX, and VALUE columns).
select empd.value:kind,
empd.value:fullName,
empd.value:age,
empd.value:gender,
empd.value:phoneNumber,
empd.value:phoneNumber.areaCode,
empd.value:phoneNumber.number ,
empd.value:children,
chldrn.value:name,
chldrn.value:gender,
chldrn.value:age,
city.value:place,
yr.value:yearsLived
from my_json emp,
lateral flatten(input=>emp.Json_data:empDetails) empd ,
lateral flatten(input=>empd.value:children, OUTER => TRUE) chldrn, -- <HERE>
lateral flatten(input=>empd.value:citiesLived) city,
lateral flatten(input=>city.value:yearsLived) yr