in nodejs how to insert the record into PostgreSQL if it does not exist?

Question

router.post('/university', function (req, res, next) {
 
   pg.connect(connectionString,function(err,client,done) {
      if(err){
          console.log("not able to get connection "+ err);
          res.status(400).send(err);
      } 

      client.query("select university_name from university where university_name = '"+req.body.university_name+"'",function(err,data)
      {
           if(data) {
             res.send({message:"exist"});
             
           }
           else
           {
             client.query("INSERT INTO university (_id, university_name, status) VALUES (nextval('university_id_seq'), '"+req.body.university_name+"', '"+req.body.status+"')", function(err, result) {
             done();
             if(err){
              console.log(err);
              res.status(400).send(err);
           }
           res.send({message : "successfully inserted"});
           
           });
           }
         });

it displays university_name as exist even it is not present on every entry, how to insert the record into PostgreSQL if does not exists?

Please show the updated code. Also, you have a SQL injection, please use parameterized queries. — jcaron
– jcaron, Commented Oct 9, 2017 at 7:28
Possible duplicate of Insert if not exists, else return id in postgresql — vitaly-t
– vitaly-t, Commented Oct 9, 2017 at 12:28

Dario · Accepted Answer · 2017-10-09 07:37:53Z

3

It depends on which DB driver you are using, anyway most common is that when SELECT query is executed, you will get result data even if records in the DB doesn't exists. Usually result object then has property rows which you should check.

In your case similar to this:

if(data.rows && data.rows.length > 0){
   // there is data in the DB
} else {
   // no data in the DB
}

answered Oct 9, 2017 at 7:37

Dario

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1 Comment

Dario Over a year ago

You're welcome. In addition you can read more about INSERT ... ON CONFLICT statement (usually known as UPSERT) and take care about possible SQL injection.

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