为什么 Postgres 谈论第 0 列； 这是什么意思？

Question

While trying to add a new subject to the subjects table, Postgres thinks I want to add something to columns 0, 1, and 3. Why?

I'm posting a new user with Postman. In the user routes, I am inserting the user object in the user table. That works.

My second step is to insert the subject in a subjects table if that subject does not exist yet.

That is where things go wrong.

This method should insert a new subject in the subjects table and return the new row:

    insertSubject(knex, newSubject) {
        return knex
            .insert(newSubject)
            .into('subjects')
            .returning('*')
            .then(rows => {
                console.log(rows)
                return rows[0]
            })
    },

Instead of doing so, I'm getting this message in Postman:

{
    "message": "insert into \"subjects\" (\"0\", \"1\", \"2\") values ($1, $2, $3) returning * - column \"0\" of relation \"subjects\" does not exist",
    "error": {
        "length": 122,
        "name": "error",
        "severity": "ERROR",
        "code": "42703",
        "position": "25",
        "file": "parse_target.c",
        "line": "1034",
        "routine": "checkInsertTargets"
    }

For reference, this is how I'm calling the above method:

    .post(jsonParser, (req, res, next) => {
        const { first_name, last_name, email, user_password, gender, tutor, student, fee, in_person, online_medium, subjects } = req.body;
        const userFields = { first_name, last_name, email, user_password, gender, tutor, student, fee, in_person, online_medium, subjects };
        const newUser = { first_name, last_name, email, user_password, gender, tutor, student, fee, in_person, online_medium };

        for (const [key, value] of Object.entries(userFields)) {
            if (value === null) {
                return res.status(400).json({
                    error: { message: `Missing ${key} in request body` }
                })
            }
        }

        const user = []
        UsersService.insertUser(
            req.app.get('db'),
            newUser
        )
        .then(res => {
            user.push(res)
            return SubjectsService.getBySubject(
                req.app.get('db'),
                subjects
            )
        })
            .then(res => {
                //console.log logs the subject I posted with postman
                console.log(subjects)
                if (typeof res === 'undefined') {
                    return SubjectsService.insertSubject(
                        req.app.get('db'),
                        subjects
                    )
                    .then(res => {
                        console.log("hihi")
                    })
                }
            })
            .then(response => {
                console.log(response)
                res
                    .status(201)
                    .location(path.posix.join(req.originalUrl, `/${user[0].id}`))
                    .json(serialize(user))
            })
            .catch(next)
    })

This is the object I sent through Postman:

        "first_name": "Felicio",
        "last_name": "Heading",
        "email": "fheadi0@nyu.edu",
        "user_password": "5u2v1E1BKrct",
        "online_medium": true,
        "in_person": true,
        "student": false,
        "tutor": true,
        "gender": "Male",
        "rating": 1,
        "fee": 25,
        "subjects": "abc"
       }

Edit: I'm only attempting to enter subject in the subject table. subjects evaluates to abc .

Answer 1

The error:

"insert into \"subjects\" (\"0\", \"1\", \"2\") values ($1, $2, $3) returning * - column \"0\" of relation \"subjects\" does not exist"

The reason is that you are telling Postgres that the table has columns "0", "1", and "2" that you want to INSERT values ($1, $2, $3) into. The error is telling you those columns don't exist in the table. Actually it stops at column "0" as it makes no sense to go any further. Best guess is you are assigning the values you which to INSERT to the column list.

Answer 2

As @AdrianKlaver noted in a comment, I needed to change the insert code. I updated it like so:

    insertSubject(knex, newSubject) {
        return knex('subjects')
            .insert({subject_name: newSubject})
            .returning('*')
            .then(rows => {
                console.log(rows)
                return rows[0]
            })
    },

And it works!