COUNT¶
The Count
aggregate function allows you to calculate the number of objects in a table, optionally satisfying some criteria or grouped by values in a column. To use the function, include Count(columnNameInDatabase)
into the list of properties requested from the server. For example, the following query retrieves the count of all movies in the database:
GET https://xxxx.backendless.app/api/data/Movie?props=Count(objectId)
The query returns the following result, notice the count
property in the returned object. The value of the property is the total count of all objects in the table:
[
{
"count": 8,
"___class": "Movie",
}
]
Using Alias¶
To change the name of the returned property from count
to a custom name, use the following syntax:
Count( columnNameInDatabase ) as customPropertyName
For example, the following query returns the total count value in the totalObjects
property:
Important
The value must be URL-encoded. The spaces are replaced with %20:
GET https://xxxx.backendless.app/api/data/Movie?props=Count(objectId)%20as%20totalObjects
The response for the query now contains the totalObjects
property:
[
{
"totalObjects": 8,
"___class": "Movie",
}
]
Grouping Results¶
Results in the response can be grouped by values from another column. To request grouping of the results, add the groupBy
parameter to the request with the value containing the name of the column. For example, the following request returns the number of movies in the database grouped by the year the movies were released:
GET https://xxxx.backendless.app/api/data/Movie?props=Count(objectId),yearReleased&groupBy=yearReleased
The response for this request contains the number of the movies grouped by the release year:
[
{
"count": 1,
"yearReleased": 1997,
"___class": "Movie",
},
{
"count": 1,
"yearReleased": 2009,
"___class": "Movie",
},
{
"count": 1,
"yearReleased": 2011,
"___class": "Movie",
},
{
"count": 1,
"yearReleased": 2012,
"___class": "Movie",
},
{
"count": 4,
"yearReleased": 2015,
"___class": "Movie",
}
]
Sorting¶
The results can be sorted using the sortBy
parameter. For example, results for the following request will be sorted by the values in the yearReleased
column in the descending order:
GET https://xxxx.backendless.app/api/data/Movie?props=Count(objectId),yearReleased&groupBy=yearReleased&sortBy=yearReleased%20DESC
To sort results by the aggregated value, assign a custom name to the column and sort by that name:
GET https://xxxx.backendless.app/api/data/Movie?props=Count(objectId)%20as%20movieCount,yearReleased&groupBy=yearReleased&sortBy=movieCount