Django - Raw query to ORM - mysql

Question

models.py
class Employees(models.Model):
emp_no = models.IntegerField(primary_key=True)
birth_date = models.DateField()
first_name = models.CharField(max_length=14)
last_name = models.CharField(max_length=16)
gender = models.CharField(max_length=1)
hire_date = models.DateField()
class Meta:
managed = False
db_table = 'employees'
class Salaries(models.Model):
emp_no = models.ForeignKey(Employees, models.DO_NOTHING, db_column='emp_no',related_name='salaries', primary_key=True)
salary = models.IntegerField()
from_date = models.DateField()
to_date = models.DateField()
class Meta:
managed = False
db_table = 'salaries'
unique_together = (('emp_no', 'from_date'),)
Mysql raw query:
SELECT `employees`.`emp_no`, `employees`.`birth_date`, `employees`.`first_name`, `employees`.`last_name`, `employees`.`gender`, `employees`.`hire_date`,
(
SELECT JSON_ARRAYAGG(
JSON_OBJECT(
'salary', `salaries`.`salary`,
'from_date', `salaries`.`from_date`,
'to_date', `salaries`.`to_date`
)
) FROM `salaries` WHERE (`employees`.`emp_no` = `salaries`.`emp_no`)
) as salaries
FROM `employees`
INNER JOIN `salaries` root_salaries ON `root_salaries`.`salary` > 60000
WHERE `employees`.`emp_no` = `root_salaries`.`emp_no` LIMIT 100 OFFSET 100
Output for raw query:
[
{
"emp_no": 10017,
"birth_date": "1958-07-06",
"first_name": "Cristinel",
"last_name": "Bouloucos",
"gender": "F",
"hire_date": "1993-08-03",
"salaries": [
{
"salary": 71380,
"to_date": "1994-08-03",
"from_date": "1993-08-03"
},
{
"salary": 75538,
"to_date": "1995-08-03",
"from_date": "1994-08-03"
}
]
},
{
"emp_no": 10018,
"birth_date": "1954-06-19",
"first_name": "Kazuhide",
"last_name": "Peha",
"gender": "F",
"hire_date": "1987-04-03",
"salaries": [
{
"salary": 55881,
"to_date": "1988-04-02",
"from_date": "1987-04-03"
},
{
"salary": 59206,
"to_date": "1989-04-02",
"from_date": "1988-04-02"
},
{
"salary": 61361,
"to_date": "1990-04-02",
"from_date": "1989-04-02"
}
]
}
]
My question is how to generate the above raw query using Django ORM.
Thanks.

Answer 1

Views.py
query_set = Employees.objects.filter(salaries__salary__gt=60000).annotate(
salaries_1=Subquery(
Salaries.objects.filter(emp_no=OuterRef('emp_no'), salary__gt=60000).values(
salaries=JSONArrayAgg(JSONObject(
salary=F('salary'),
from_date=F('from_date'),
to_date=F('to_date')
))))
).distinct()[100:200]
employee_ser = EmployeesWithSalaryGroupSerializer(query_set, many=True)
data = employee_ser.data
Serializers.py
class EmployeesWithSalaryGroupSerializer(serializers.Serializer):
emp_no = serializers.IntegerField()
birth_date = serializers.DateField()
first_name = serializers.CharField()
last_name = serializers.CharField()
gender = serializers.CharField()
hire_date = serializers.DateField()
salaries_1 = serializers.JSONField()
def to_representation(self, instance):
ret = super(EmployeesWithSalaryGroupSerializer, self).to_representation(instance=instance)
ret['salaries'] = json.loads(instance.salaries_1)
ret.pop('salaries_1')
return ret