How do I convert a complex GROUP BY to Sequelize? - postgresql

Question

My SQL query is
SELECT t."id", t."topicText", COUNT(t."id") AS topicCount
FROM "WorkbookQuestions" wq, "Workbooks" w, "Questions" q, "Topics" t
WHERE w."StudentId" = 3
AND wq."QuestionId" = q."id"
AND wq."WorkbookId" = w."id"
AND q."TopicId" = t."id"
GROUP BY "t"."id"
ORDER BY "topiccount" DESC
How can I write this in Sequelize code so I can avoid writing SQL directly? Or is it not possible?
This is what I've tried (unsuccessfully) so far:
db.WorkbookQuestion.findAll({
attributes: ['Topics.id', [db.sequelize.fn('COUNT', db.sequelize.col('Topics.id'))], 'TopicCount'],
include: [
{
model: db.Workbook,
where: {
StudentId: newWorkbook.StudentId,
SubjectId: newWorkbook.SubjectId
}
}, {
model: db.Question,
include: [
{
model: db.Topic
}
]
}
],
group: ['Topics.id']
});

Answer 1

Just by looking at it, i would write the code like this
db.Workbook.findAll({
attributes: ['wbquestion.question.topic.id', [db.sequelize.fn('COUNT', db.sequelize.col('wbquestion.question.topic.id'))], 'topiccount'],
include: [
{
model: db.WorkbookQuestion,
as: wbquestion,
where: {
id: wbquestion.workbookId
},
include: [
model: db.Question,
as: question,
where: {
id: wbquestion.questionId
},
include: [
model: db.Topic,
as: topic,
where: {
id: question.topicId
}
]
]
}
],
where: {
studentId : 3
}
group: ['topic.id']
});
Maybe you can get more readable code by defining the models and relations separately and using eager loading afterwards.
Edit:
Generated the migrations and models
node_modules/.bin/sequelize model:create --name Student --attributes firstName:string,lastName:string
node_modules/.bin/sequelize model:create --name Topic --attributes topicText:string
node_modules/.bin/sequelize model:create --name Question --attributes TopicId:integer
node_modules/.bin/sequelize model:create --name Workbook --attributes studentId:integer
node_modules/.bin/sequelize model:create --name WorkbookQuestion --attributes QuestionId:integer,WorkbookId:integer
A simple program for testing the query in console log.
var Sequelize = require("sequelize");
var models = require('./models/index');
models.WorkbookQuestion.belongsTo(models.Question, {foreignKey: 'QuestionId'});
models.WorkbookQuestion.belongsTo(models.Workbook, {foreignKey: 'WorkbookId'});
models.Question.hasOne(models.WorkbookQuestion);
models.Workbook.hasOne(models.WorkbookQuestion);
models.Workbook.belongsToMany(models.Question, {through: models.WorkbookQuestion});
models.Workbook.belongsToMany(models.Topic, {through: models.Question});
var res = models.Workbook.findAll({
attributes: ['topicId', Sequelize.fn('count', Sequelize.col('topiccount'))],
include: [models.WorkbookQuestion, models.Question, models.Topic],
where: {
studentId: 3
},
group: ['topic.id']
}).then(function(data) {
console.log(data);
}).catch(function(err) {
console.trace(err);
});
The result is:
SequelizeDatabaseError: column Topics.Question.WorkbookId does not exist
Maybe you can fix the relations between the models or you should create the query not using findAll functionality.