Two client queries in that same function

Two client queries in that same function

Problem

I have a question about if it is right to do two client.queries one right after the other. I am trying to build a REST API. Example:

client.query("select waiters_id from waiters", function(err, result){
                     if(err){
                         res.json({success: false, msg: "error"});
                     }
                     if(result.rows.length === 0){
                         done();
                         res.json({success: false, msg: "error"});
                     } else{
                         if(results.rows[0].waiter_id === req.body.waitid){
                                 done();
                                 res.json({success: true, msg: "proceed"});
                             }
                         client.query("insert into waiters",function(err, result){
                              // MORE CODE
                         });

I am trying to check if there is a waiter in the waiters table, then insert some specific information into that waiter in that waiters table if there is a waiter. If there is a better way to do this please let me know. I don’t want to lose performance. Thanks

Problem courtesy of: user3192435

Solution

This question really has more to do with SQL then nodejs/express. SQL provides you with the ability to use if statements to make logical assertions about your results:

client.query(
  "IF EXISTS (SELECT * FROM waiters WHERE waiters_id='SomeValue')
      UPDATE waiters SET (...) WHERE waiters_id='SomeValue'
   ELSE
      INSERT INTO waiters VALUES (...)
   SELECT * FROM waiters",
  function (err, result) {
     // do something with results here     
  }
);

Which is essentially the same control logic you are trying to build with nodejs. Using the above would eliminate the need for another query.

Solution courtesy of: srquinn

Discussion

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