REST API Javascript How to write condition that checks if SQL query returns 0 rows

Question

I have db airport, there is TABLE tourists and in it COLUMN: id and also i have TABLE: flights, and there is column: listoftouristsbyid which is array of integers. I need to check if i passed to REST API request integer that is id of Tourist that not EXISTS. Means there is no tourist with given id (id is primary, autoincrementing key). I wrote something like that:

app.post('/flights', function(req, res) {
    pool.connect(function(err,client,done) {
        if(err) {
            return console.log("Error fetching clients", err);
        }
        client.query("SELECT tourists.id FROM tourists WHERE tourists.id = " + req.body.listoftouristsbyid[i], function (err, result) {
            done();
            if (result.rows === 0) {
                return console.log("Tourist "+req.body.listoftouristsbyid[i]+" you want to add does not exist" + err);
            }
        })
        client.query('INSERT INTO flights(departuredate, arrivaldate, numberofseats, listoftouristsbyid, ticketprice) VALUES($1, $2, $3, $4, $5)', 
            [req.body.departuredate, req.body.arrivaldate, req.body.numberofseats, req.body.listoftouristsbyid, req.body.ticketprice]);
        done();
        res.redirect('/flights');
    })
})

I know ITS A VALID QUERY, because when i type it in PSQL shell it returns

airport=#                                                                  
SELECT tourists.id FROM tourists WHERE tourists.id = 15;
 id 
----
(0 rows)

But its not working as javascript code - means code should terminate with error, but condition is not fulfiled. How do i write condition in Javascript that catches when SELECT tourists.id FROM tourists WHERE tourists.id = 15 gives 0 rows?

Has the connected user permissions to read the auto incremented key column? — Teemu
– Teemu, Commented Sep 27, 2018 at 12:04

Torab Shaikh · Accepted Answer · 2018-09-27 12:20:43Z

1

In MySQL, When you perform a read operation, It will give you value in Array. So, get the length of the result array by result.length check if it is equal to zero.

When you perform a write or update operation, the result will contain a property affectedRows Which will tell you the number of rows affected. Print the result using console.sql('%j', result) and See if there is some option in PostGreSQL(Most probably there is).

answered Sep 27, 2018 at 12:20

Torab Shaikh

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