Counting Associated Entries With Sequelize

Answer :

Use findAll() with include() and sequelize.fn() for the COUNT:

Location.findAll({
    attributes: { 
        include: [[Sequelize.fn("COUNT", Sequelize.col("sensors.id")), "sensorCount"]] 
    },
    include: [{
        model: Sensor, attributes: []
    }]
});

Or, you may need to add a group as well:

Location.findAll({
    attributes: { 
        include: [[Sequelize.fn("COUNT", Sequelize.col("sensors.id")), "sensorCount"]] 
    },
    include: [{
        model: Sensor, attributes: []
    }],
    group: ['Location.id']
})

Location.findAll({
        attributes: { 
            include: [[Sequelize.fn("COUNT", Sequelize.col("sensors.id")), "sensorCount"]] 
        },
        include: [{
            model: Sensor, attributes: []
        }]
    });

and it works. but when i add "limit", i got error: sensors undefined

For Counting associated entries with Sequelize

Location.findAll({
    attributes: { 
        include: [[Sequelize.fn('COUNT', Sequelize.col('sensors.location')), 'sensorCounts']] 
    }, // Sequelize.col() should contain a attribute which is referenced with parent table and whose rows needs to be counted
    include: [{
        model: Sensor, attributes: []
    }],
    group: ['sensors.location'] // groupBy is necessary else it will generate only 1 record with all rows count
})

Note :

Some how, this query generates a error like sensors.location is not exists in field list. This occur because of subQuery which is formed by above sequelize query.

So solution for this is to provide subQuery: false like example

Location.findAll({
        subQuery: false,
        attributes: { 
            include: [[Sequelize.fn('COUNT', Sequelize.col('sensors.location')), 'sensorCounts']] 
        },
        include: [{
            model: Sensor, attributes: []
        }],
        group: ['sensors.location']
    })

Note:
**Sometime this could also generate a error bcz of mysql configuration which by default contains only-full-group-by in sqlMode, which needs to be removed for proper working.

The error will look like this..**

Error : Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'db.table.id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

So to resolve this error follow this answer

SELECT list is not in GROUP BY clause and contains nonaggregated column .... incompatible with sql_mode=only_full_group_by

Now this will successfully generate all associated counts

Hope this will help you or somebody else!