Question

我是node.js的新手，我想将查询的输出输入到另一个查询请帮助

 pool.getConnection(function(err, connection) {
   connection.query("select * from tbl_chat", function(err, rows) {
       console.log(rows[0]['from_id']);
       var fromid = rows[0]['from_id'];
   });
   console.log(fromid);//throws ReferenceError: fromid is not defined
   console.log(rows[0]['from_id']);// throws ReferenceError: rows is not defined

  //I want to use the fromid in the following query 

   /*connection.query("select * from tbl_chat where from_id=?",[fromid], function(err, rows) {
       console.log(rows[0]['from_id']);
   });*/
 });

Answer 1

NodeJs数据库查询是异步的，因此您必须将您的console.log放在回调中，或者使用promises执行。

试一试：

 pool.getConnection(function(err, connection) {
   connection.query("select * from tbl_chat", function(err, rows) {
       console.log(rows[0]['from_id']);
       var fromid = rows[0]['from_id'];
       console.log(fromid);
       console.log(rows[0]['from_id']);
       connection.query("select * from tbl_chat where from_id=?",[fromid], function(err, rows) {
           console.log(rows[0]['from_id']);
       });
   });
 });

Node.js：如何将一个查询的输出用于另一个查询的输入

1 个答案: