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POSynchronous database queries with Node.js
 

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    <p>I have a Node.js/Express app that queries a MySQL db within the route and displays the result to the user. My problem is how do I run the queries and block until both queries are done before redirecting the user to the page they requested?</p> <p>In my example I have 2 queries that need to finish before I render the page. I can get the queries to run synchronously if i nest query 2 inside the 'result' callback of query 1. This however will become very convoluted when the number of queries increase.</p> <p>How do I go about running multiple (in this case 2) database queries synchronously without nesting the subsequent query in the prior query's 'result' callback?</p> <p>I've looked at the 'Flow control / Async goodies' in the Node modules and tried flow-js but I can't get it to work with the async queries.</p> <p>Listed below are the 2 queries that I'm attempting to execute from the '/home' route. Can the Node experts explain the 'right' way to do this.</p> <pre><code>app.get('/home', function (req,res) { var user_array = []; var title_array = []; // first query var sql = 'select user_name from users'; db.execute(sql) .addListener('row', function(r) { user_array.push( { user_name: r.user_name } ); }) .addListener('result', function(r) { req.session.user_array = user_array; }); // second query var sql = 'select title from code_samples'; db.execute(sql) .addListener('row', function(r) { title_array.push( { title: r.title } ); }) .addListener('result', function(r) { req.session.title_array = title_array; }); // because the queries are async no data is returned to the user res.render('home.ejs', {layout: false, locals: { user_name: user_array, title: title_array }}); }); </code></pre>
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    1. COI .. uh ... I think you're doing this completely wrong ... The whole point is for asynchronicity. It's actually a much better programming model. Have you any understanding of what node.js is for? It's to allow you to use evented callbacks to reduce the amount of spintime on individual threads, thus utilizing the system more. I really suggest you adopt the "do things in the callback" model, as that is the intent. Or switch to Ruby.
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    2. COSo how would you go about doing multiple async queries and return the data to the EJS view?
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    3. COIn callbacks. But that's just me.
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