CODEWITHSUNDEEP
sqlnode.jsnode-mysql
GleneaMan
GleneaMan

Reputation: 177

How to input a NodeJS variable into an SQL query

I want to write an SQL query that contains a NodeJS variable. When I do this, it gives me an error of 'undefined'.

I want the SQL query below to recognize the flightNo variable. How can a NodeJS variable be input into an SQL query? Does it need special characters around it like $ or ?.

app.get("/arrivals/:flightNo?", cors(), function(req,res){
var flightNo = req.params.flightNo;

connection.query("SELECT * FROM arrivals WHERE flight = 'flightNo'", function(err, rows, fields) {

Upvotes: 13

Views: 47678

Answers (2)

Fellipe Sanches
Fellipe Sanches

Reputation: 8125

From ES6 you can use template literals with ${expression}.

Template literals are literals delimited with backtick (`) characters, allowing multi-line strings and interpolation with expressions.

Use like this:

connection.query(`
SELECT * 
FROM arrivals 
WHERE flight = ${flightNo}
`, //rest of your code

Upvotes: 0

Dave
Dave

Reputation: 1987

You will need to put the value of the variable into the SQL statement.

This is no good:

"SELECT * FROM arrivals WHERE flight = 'flightNo'"

This will work, but it is not safe from SQL injection attacks:

"SELECT * FROM arrivals WHERE flight = '" + flightNo + "'"

To be safe from SQL injection, you can escape your value like this:

"SELECT * FROM arrivals WHERE flight = '" + connection.escape(flightNo) + "'"

But the best way is with parameter substitution:

app.get("/arrivals/:flightNo", cors(), function(req, res) {
  var flightNo = req.params.flightNo;

  var sql = "SELECT * FROM arrivals WHERE flight = ?";
  connection.query(sql, flightNo, function(err, rows, fields) {
  });
});

If you have multiple substitutions to make, use an array:

app.get("/arrivals/:flightNo", cors(), function(req, res) {
  var flightNo = req.params.flightNo;
  var minSize = req.query.minSize;

  var sql = "SELECT * FROM arrivals WHERE flight = ? AND size >= ?";
  connection.query(sql, [ flightNo, minSize ], function(err, rows, fields) {
  });
});

Upvotes: 26

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