问题描述
这是我第一次使用tedious.js，我还是不太明白。我主要是查看他们的文档 here。
以下是POST方法中的逻辑。
这是我在 express.js 中添加“标签”的 post 方法
// POST add tags
router.post('/tag',function(req,res){
// get the body
const data = req.body;
// sql query to check if the tag already exists for the given id or not.
let sql = `SELECT * FROM tags WHERE corporate_statement_link_id = @corporate_statement_link_id and name = @name FOR JSON PATH`;
// sql query to insert the tag in the database
let query = `INSERT INTO tags (corporate_statement_link_id,name) VALUES(@corporate_statement_link_id,@name)`;
console.log("Getting tags");
try {
console.log("Checking if the tag '",data.name,"' exists for ",data.corporate_statement_link_id,".");
//This is where I'm using the tedious to make connection to Azure database
var conn = sqldb.createConnection();
var request = sqldb.createRequest(sql,conn);
request.addParameter('corporate_statement_link_id',TYPES.Int,data.corporate_statement_link_id);
request.addParameter('name',TYPES.VarChar,data.name);
//=========>>>
// This is where I'm not so sure what's happening and if I can call it this way.
// The reason I'm trying this is because var "request" is always undefined since it's done async?. so,even though the tag exists in the database,the code below to add the tag still runs.
var result = sqldb.runQuery(request,conn,res,'{}').then(d => {
console.log(d);
});
// console.log("Result: ",result);
if(!request){
console.log('the tag already exists')
res.status(300).send("Tag already exist.");
} else {
console.log("Tag ","doesn't exist.")
console.log("Creating tag");
// This is to add the tag to the database
conn = sqldb.createConnection();
request = sqldb.createRequest(query,conn);
request.addParameter('corporate_statement_link_id',data.corporate_statement_link_id);
request.addParameter('name',data.name);
result = sqldb.runQuery(request,'{}');
console.log("Result: ",result);
return result;
}
} catch(err){
res.send(err);
}
Azure 数据库连接
'use strict'
// function to create connection to the sql database
function createConnection(){
var AzureConfig = {
authentication: {
options: {
userName: "username",password: "password"
},type: "default"
},server: "server",options: {
database: "database",encrypt: true,validateBulkLoadParameters: true
}
};
// create connection to the database
var Connection = require('tedious').Connection;
var connection = new Connection(AzureConfig);
return connection;
}// end create connection
// create query request
function createRequest(query,connection){
var Request = require('tedious').Request;
console.log("Creating new request");
var req = new Request(query,function(err,rowCount) {
if(err){
console.log(err);
output.write(err);
}
connection && connection.close();
});
console.log("Request created..");
return req;
}
// Running the query
function runQuery(query,connection,output,defaultContent){
var request = query;
if(typeof query == 'string'){
request = createRequest(query,connection);
}
console.log("It's not a query but a request..");
var empty = true;
request.on('row',function(columns){
console.log("Checking and running the row..");
if(empty){
console.log("Response fetched from sql Database.");
empty = false;
}
console.log("Columns found: ",columns[0].value);
// console.log(output);
output.write(columns[0].value);
// console.log("returning data");
// data.push(columns[0].value);
});
request.on('done',function(rowCount,more,rows){
console.log("The request is done..");
console.log(rowCount,"rows returned");
// output.end();
_OnDone(empty,defaultContent,output);
});
request.on('doneProc',rows){
console.log("The request procedure is done..");
_OnDone(empty,output);
console.log(rowCount,"rows returned");
// output.end();
});
console.log("Executing request");
executeRequest(request,connection);
}
function _OnDone(empty,output){
if(empty){
output.write(defaultContent);
console.log('No results from database - default content is returned.');
}
try{
console.log('Closing Http Response output.');
// console.log("Output: ",output);
output.end();
} catch(err){
// output.write(err);
console.error(err);
}
}
// execute request to pull the data
function executeRequest(request,connection){
console.log("checking the connection..");
connection.on('connect',function(err){
if(err){
console.log(err);
//output.write(err);
}
console.log("request executing...");
console.log("Request: ",request);
connection.execsql(request);
});
}
module.exports.createConnection = createConnection;
module.exports.createRequest = createRequest;
module.exports.executeRequest = executeRequest;
module.exports.runQuery = runQuery;
Checking and running the row..
Response fetched from sql Database.
Columns found: [{"corporate_statement_link_id":3,"name":"black-lives-matter","id":11},{"corporate_statement_link_id":3,"name":"edi","id":12},"name":"test","id":13},"name":"test2","id":14},"name":"test3","id":23},"id":24}]
The request procedure is done..
Closing Http Response output.
undefined rows returned
GET /api/v1/statements/tags/3 200 353.227 ms - -
Getting tags
Checking if the tag ' test4 ' exists for 3 .
Creating new request
Request created..
It's not a query but a request..
Executing request
checking the connection..
POST /api/v1/statements/tag 200 27.657 ms - 2
request executing...
Request: Request {
_events: [Object: null prototype] {
row: [Function],done: [Function],doneProc: [Function]
},_eventsCount: 3,_maxListeners: undefined,sqlTextOrProcedure: 'SELECT * FROM tags WHERE corporate_statement_link_id = @corporate_statement_link_id and name = @name FOR JSON PATH',parameters: [
{
type: [Object],name: 'corporate_statement_link_id',value: 3,output: false,length: undefined,precision: undefined,scale: undefined
},{
type: [Object],name: 'name',value: 'test4',scale: undefined
}
],parametersByName: {
corporate_statement_link_id: {
type: [Object],name: {
type: [Object],scale: undefined
}
},originalParameters: [],preparing: false,canceled: false,paused: false,userCallback: [Function],handle: undefined,error: undefined,connection: undefined,timeout: undefined,rows: undefined,rst: undefined,rowCount: undefined,callback: [Function],[Symbol(kCapture)]: false
}
The request procedure is done..
No results from database - default content is returned.
Closing Http Response output.
undefined rows returned
events.js:292
throw er; // Unhandled 'error' event
^
Error [ERR_STREAM_WRITE_AFTER_END]: write after end
at write_ (_http_outgoing.js:629:17)
at ServerResponse.write (_http_outgoing.js:621:15)
at _OnDone (C:\Users\shresthas\source\repos\statement-rater-app\routes\azure-db.js:99:16)
at Request.<anonymous> (C:\Users\shresthas\source\repos\statement-rater-app\routes\azure-db.js:87:9)
at Request.emit (events.js:315:20)
at Request.emit (C:\Users\shresthas\source\repos\statement-rater-app\node_modules\tedious\lib\request.js:154:18)
at Parser.<anonymous> (C:\Users\shresthas\source\repos\statement-rater-app\node_modules\tedious\lib\connection.js:1323:19)
at Parser.emit (events.js:315:20)
at Parser.<anonymous> (C:\Users\shresthas\source\repos\statement-rater-app\node_modules\tedious\lib\token\token-stream-parser.js:35:14)
at Parser.emit (events.js:315:20)
Emitted 'error' event on ServerResponse instance at:
at writeAfterEndNT (_http_outgoing.js:684:7)
at processticksAndRejections (internal/process/task_queues.js:85:21) {
code: 'ERR_STREAM_WRITE_AFTER_END'
}
如何解决，当找到标签时，它绕过插入语句返回给客户端，但如果标签不存在，我想插入它然后将标签发送给客户端？
>解决方法
不是运行两个单独的查询，一个用于 SELECT，另一个用于 INSERT，这实际上需要显式事务以确保一切始终保持一致，您只需一个查询即可执行所有内容，这也将使代码更简单：
with cte as
(
select * from ( values (4,'tag6') ) as t(csid,[name])
)
insert into dbo.[tags_65648013] (corporate_statement_link_id,[name])
output inserted.*
select * from cte
where not exists (
select * from dbo.[tags_65648013] where corporate_statement_link_id = cte.csid and [name] = cte.[name]
)
您可以使用类似的方法测试代码：
drop table if exists dbo.tags_65648013;
create table dbo.tags_65648013
(
corporate_statement_link_id int not null,[name] nvarchar(50) not null,)
go
create clustered index ixc on dbo.tags_65648013(corporate_statement_link_id);
go
insert into dbo.[tags_65648013] values
(1,'tag1'),(1,'tag2'),'tag3'),(2,'tag4'),(3,'tag5')
go
select * from dbo.[tags_65648013]
go
更新：由于 OUTPUT 不支持 FOR JSON，您需要将结果发送到 @temp 表中并从那里查询：
declare @result as table (id int,[name] nvarchar(50));
with cte as
(
select * from ( values (4,'tag66') ) as t(csid,[name])
)
insert into @result
select * from (
insert into dbo.[tags_65648013] (corporate_statement_link_id,[name])
output inserted.*
select * from cte
where not exists (
select * from dbo.[tags_65648013] where corporate_statement_link_id = cte.csid and [name] = cte.[name]
)) r
select * from @result for json auto;
在@Mike'Pomax'Kamermans 的大力帮助下，我能够重新访问我的代码并解决我遇到的问题。非常感谢@Mike'Pomax'Kamermans。你向我展示路径的方式对帮助我理解问题非常有帮助 - 比简单地给出答案更好。
另外，还要感谢@mauridb，他为我提供了一种更酷、更好的编写 SQL 查询的方法。
这是我的 azure-sql.js 现在的样子：
'use strict'
// function to create connection to the SQL database
function createConnection(){
var AzureConfig = {
authentication: {
options: {
userName: "username",password: "password"
},type: "default"
},server: "server",options: {
database: "database",encrypt: true,validateBulkLoadParameters: true
}
};
// create connection to the database
var Connection = require('tedious').Connection;
var connection = new Connection(AzureConfig);
return connection;
}// end create connection
// function to configure request to be sent to the SQL server
function configureRequest(sql,conn,parameters){
var request = createRequest(sql,conn);
parameters.forEach(function(param){
request.addParameter(param.name,param.type,param.data);
});
return request;
}
// create query request
function createRequest(query,connection){
var Request = require('tedious').Request;
var req = new Request(query,function(err,rowCount) {
if(err){
console.log(err);
}
connection && connection.close();
});
return req;
}
// Running the query
function runQuery(query,connection,callback){
var request = query;
if(typeof query == 'string'){
request = createRequest(query,connection);
}
var values = '';
// the rows are returned as a json array. Since it's sent in a batch,// different events are raised.
// So the values are concatenated to create a single JSON object
request.on('row',function(column) {
values += column[0].value;
});
// if anything specific needs to be done after the process is complete
request.on('done',function(rowCount,more,rows){
// check if the SQL Server returned anything
values = checkValues(values);
callback(values);
});
// if anything specific needs to be done after the stored procedure is complete
// however,if we use connection.execSql(),it emits doneProc instead of done.
request.on('doneProc',rows){
// check if the SQL Server returned anything
values = checkValues(values);
callback(values);
});
try {
executeRequest(request,connection);
} catch(err){
throw err
}
// return the values parsed as JSON
// return JSON.parse(values);
return values;
}
// function to check values if the response from SQL Server is empty
function checkValues(values){
if (values === ''){
// needs to be set to null if the SQL Server return nothing.
// This is required to ensure JSON is correctly parsed.
values = null;
}
return values;
}
// execute request to pull the data
function executeRequest(request,connection){
connection.on('connect',function(err){
if(err){
console.log(err);
res.send(err);
}
connection.execSql(request);
});
}
module.exports.createConnection = createConnection;
module.exports.createRequest = createRequest;
module.exports.executeRequest = executeRequest;
module.exports.configureRequest = configureRequest;
module.exports.runQuery = runQuery;
在此之后，其他一切就都到位了。然后，我只需更新 router 以便它可以将数据返回给客户端。
// POST add tags
router.post('/tag',function(req,res){
const data = req.body;
let sql = `declare @result as table (id int,corporate_statement_link_id int,[name] nvarchar(50));
with cte as
(
select * from ( values (@corporate_statement_link_id,@name) ) as t(corporate_statement_link_id,[name])
)
insert into @result
select * from (
insert into dbo.tags (corporate_statement_link_id,[name])
output inserted.id,inserted.corporate_statement_link_id,inserted.name
select * from cte
where not exists (
select * from dbo.[tags] where corporate_statement_link_id = cte.corporate_statement_link_id and [name] = cte.[name]
)) r
select * from @result for json auto;`;
try {
var conn = sqldb.createConnection();
// var request = sqldb.createRequest(sql,conn);
var parameters = [
{
'name': 'corporate_statement_link_id','type': TYPES.Int,'data': data.corporate_statement_link_id
},{
'name': 'name','type': TYPES.NVarChar,'data': data.name
}
]
var request = sqldb.configureRequest(sql,parameters);
// using the query above,check if the tag already exists or not,// and if
sqldb.runQuery(request,(result,err) => {
if(err){
res.send(500).send(err);
}
// The query above checks if the tag exists or not and inserts if it is not
// If the data is already present in the database,then it'll return null.
// otherwise,it'll return the data that is inserted.
if(result === null){
res.status(409).send("The tag already exists");
} else {
res.send(JSON.parse(result));
}
});
} catch(err){
res.send(err);
}
});