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javascriptmysqlnode.jsnode-mysql

When to use ?? and ? as placeholders in node-mysql for building a query?

I am looking at some examples in node-mysql https://github.com/felixge/node-mysql

I am confused over when to use ?? and ? as placeholders in constructing a query.

An example is here;

var userId = 1;
var columns = ['username', 'email'];
var query = connection.query('SELECT ?? FROM ?? WHERE id = ?', [columns, 'users', userId], function(err, results) {
  // ...
});

console.log(query.sql); // SELECT `username`, `email` FROM `users` WHERE id = 1

How do I know when to use ?? and when to use ? ?

Solution

  • ?? is for identifiers. ? is for values.

    values are variables. identifiers are contents of variables or constants.

    For more details, see links below

    https://github.com/felixge/node-mysql#escaping-query-values https://github.com/felixge/node-mysql#escaping-query-identifiers

    Credit goes to t.niese's comment.