NodeJS / MySQL将查询结果返回给变量

I use NodeJS to insert data to a table with many to many relationship, and I want to include two foreign keys when I insert data into the table this is how my code looks:

我使用NodeJS将数据插入到具有多对多关系的表中，并且我想在将数据插入表中时包含两个外键，这就是我的代码的外观：

con.query("SELECT * FROM Transaction WHERE TransactionID > 1", function(err, res) {
    if (err) {
      throw (err);
    } else if (res.length > 0) {
      console.log("Transaction already exit");
    } else {
      var transactionID;
      var filePK;
con.query("SELECT Filename FROM File WHERE Filename = ?", fileName, function(err, res) {
      if (err) throw err;
      filePK = JSON.stringify(res);
});
con.query("SELECT TransactionDescriptionPK FROM TransactionDescription WHERE TransactionDescriptionPK > 0", function(err, res) {
      if (err) throw err;
      //console.log(res);
      transactionID = res;
});
var tran = {
    TransactionID: data.ID,
    TransactionDate: data.Description,
    Amount: data.Amount

};
con.query("INSERT INTO Transaction SET ?", tran, function(err, res) {
    if (err) throw err;
});       

How I return the results from those queries so I can add them to the tran object?

我如何从这些查询中返回结果，以便将它们添加到tran对象中？

1 个解决方案

#1

You can use async.parallel

您可以使用async.parallel

async.parallel([
  function(callback) {
    // you can directly pass the parallel callback to mysql query
    // if you don't need to do anything else
    return con.query(
      "SELECT * FROM Transaction WHERE TransactionID > 1",
      callback
    );
  },
  function(callback) {
    // otherwise, just do you what you want (here JSON.stringify)
    // then don't forget to return the parallel callback
    return con.query(
      "SELECT Filename FROM File WHERE Filename = ?", 
      fileName,
      function(err, res) {
        if (err)
          return callback(err);
        const filePK = JSON.stringify(res);
        return callback(null, filePK);
      }
    );
  },
  function(callback) {
    return con.query(
      "SELECT TransactionDescriptionPK FROM TransactionDescription WHERE TransactionDescriptionPK > 0",
      callback
    );
  },
], function(err, data) {
  // if any mysql queries above encounter an error,
  // it calls the parallel final callback and stops other functions

  // without errors, data looks like :
  // data[0] equals mysql result object of the first query
  // data[1] equals filePK const
  // data[2] equals mysql result object of the last query

  const tran = {
    TransactionID: data[0][0].ID,
    TransactionDate: data[0][0].Description,
    // Amount: data.Amount // don't know where the amount come from,
                           // but you get the idea
  };
  con.query(
    "INSERT INTO Transaction SET ?",
    tran,
    function(err, res) {
      if (err)
        throw err;
      // ...
    }
  );
});