Query cosmosDB: get last element in array - azure

Question

i have document like this:
{ "id": ....,
"Title": ""title,
"ZipCodes": [
{
"Code": "code01",
"Name": "Name01"
},
{
"Code": "code02",
"Name": "Name02"
},
{
"Code": "code03",
"Name": "Name03"
} ],
"_rid": .......,
"_self": .......,
"_etag": ......,
"_attachments": "attachments/",
"_ts": ......
i was used to command
select c.id, c.ZipCodes[ARRAY_LENGTH (c.ZipCodes) -1] as ZipCodes from c
But i got error, how can i query last element ZipCodes in cosmos DB.

Answer 1

You can use ARRAY_SLICE for this. When passed -1 it returns an array containing the last element of the original array. Then index into that with [0] to get the single element contained (i.e. the zip code itself.)
SELECT c.id,
ARRAY_SLICE(c.ZipCodes,-1)[0] AS LastZipCode
FROM c

Answer 2

There is no way using select you can query the subdocument , i think you should use the where condition as follows,
SELECT value udf.sortZipCode(c.ZipCodes)
from c where c.id=2 and c.Title='title'
However, here is a user defined function (UDF) that will do the trick:
function sortZipCode(ZipCode) {
function compareTimeStamps(a, b) {
return a.TimeStamp - b.TimeStamp; //implement your logic
}
return scanLog.sort(compareTimeStamps);
}

Answer 3

But i got error, how can i query last element ZipCodes in cosmos DB.
I agree with Sajeetharan mentioned that we could use the UDF to do that. And we could do that with UDF easily.
UDF code
function userDefinedFunction(zipcodes){
return zipcodes[zipcodes.length-1];
}
SQL query:
SELECT c.id,c.Title,udf.GetLastRecord(c.ZipCodes) as ZipCodes FROM c
Test Result: