Question

我有一个使用node-oracledb连接到Oracle的Node / Express.js应用程序。

我正在尝试向我的视图返回多个查询，但是我在Node-Oracle项目中找到的所有示例都是针对单个查询的。 https://github.com/oracle/node-oracledb/tree/master/examples

网上有各种各样的信息，但是我找不到与这个确切情况相关的任何信息，我可以开始工作。我找到的最接近的是这个问题：oracledb chaining sql call using promises被带到Github并没有真正回答。

到目前为止我的工作代码是：

var express = require('express');
var router = express.Router();
var oracledb = require('oracledb');

/* GET home page. */
router.get('/', function(req, res, next) {

  oracledb.getConnection()
  .then(function(connection) {
    return connection.execute(
      "SELECT note_id, name " +
        "FROM notes " +
        "WHERE note_id = :did",
      [1234]
    )
    .then(function(result) {
        res.render('index', { title: 'Express', table: result });
        return connection.close();
    }).catch(function(err) {
        console.log(err.message);
        return connection.close();
    })
  })
  .catch(function(err) { console.log(err.message); })

});

module.exports = router;

如何使用多个查询完成此工作并将结果传递给模板？

res.render('index', { title: 'Express', table: result, table2: result2 });

编辑：我的示例基于：https://github.com/oracle/node-oracledb/blob/master/examples/promises.js

Answer 1

您可以使用Bluebird或async promises库来执行此操作。

使用Bluebird您的代码可以修改如下：

router.get('/', function(req, res, next) {

    var getConnectionP = oracledb.getConnection();

    getConnectionP.then(function(connection) {

//Defining each query as a separate promise i.e query1P and query2P as both of them returns a promise

      var query1P = connection.execute(
          "SELECT note_id, name " +
            "FROM notes " +
            "WHERE note_id = :did",
          [1234]
        );

      var query2P = connection.execute(
          "SELECT note_id, name " +
            "FROM notes " +
            "WHERE note_id = :did",
          [5678]
        );

//Promise.join as the name says, gets resolved only when both the promises passed to it gets resolved and their results are available in the "spread" function callback as shown below : 

      Promise.join(query1P, query2P).spread(function (result, result2){
        res.render('index', { title: 'Express', table: result, table2: result2 });
        return connection.close();
      })
      .catch(function (err){
        console.log(err.message);
        return connection.close();
      });
    });
});

module.exports = router;

Answer 2

如果查询执行的顺序对您无关紧要，您可以使用Promise.all()，如下所示：

Promise.all([
    connection.execute(query1),
    connection.execute(query2),
    ...
])
.then((results) => {
    // => results is an array containing the results from each query
});

如何使用Node promises从Oracle返回多个结果集

2 个答案: