How to read sql data from table and make into a variable in nodejs?

Question

Using MSSQL module, I've been trying to view the create two functions, primarily one to read the data off the database table and make it into a variable. The other will write data from an get request and update the database table.

I have the following for reading the data but I do not get any response once logged in, unsure what I'm doing wrong.

let id = {};
let date = {};
let response = {};

let readLoggerData = function(err) {
  if (err) throw err;
  con.query('SELECT * FROM Logging ORDER BY Date DESC;'),
    function(id, response, date) {
      if (response) {
        id = request.query('SELECT TOP 1 id from Logging;');
        date = request.query('SELECT TOP 1 Date FROM Logging;');
        response = request.query('SELECT TOP 1 Response from Logging;');
      };
    };
};
console.log(id);
});

MortenMoulder · Accepted Answer · 2018-07-31 07:08:22Z

1

When you call something asynchronous, you need to wait for it to be done. Your console.log() gets called immediately after the code runs, but the con.query() might take a couple of seconds.

To solve it: Move the console.log() into the function() part of the con.query() function to fix your problem. I've also allowed myself to rewrite it a bit, so it uses ES6 syntax (basically just removing the functions). You should consider doing that in the future.

let id = {};
let date = {};
let response = {};

let readLoggerData = err => {
    if (err) throw err;
    con.query('SELECT * FROM Logging ORDER BY Date DESC;'),
        (id, response, date) => {
            if (response) {
                id = request.query('SELECT TOP 1 id from Logging;');
                date = request.query('SELECT TOP 1 Date FROM Logging;');
                response = request.query('SELECT TOP 1 Response from Logging;');

                console.log(id);
            };
        };
};

Oh and you have a syntax error as well. The last ) is invalid.

answered Jul 31, 2018 at 7:08

MortenMoulder

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1 Comment

Fahad Hossain Over a year ago

Thank you so much for this! I'm still getting a hang of the async functions and really appreciate the insight.

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