如何在验证数据库中不存在数据后使用 tedious.js 在 Azure SQL 中插入数据？
How to insert data in Azure SQL using tedious.js after verifying that the data doesn't exists in the database?
第一次使用tedious.js，还不是很懂。我主要查看他们的文档 here.
下面是POST方法中的逻辑。
- 检查给定语句 id 的标签是否已经存在
- 如果标签存在，return消息给客户端
- 如果标签不存在，请将标签插入数据库。
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 ",data.name, "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', TYPES.Int, data.corporate_statement_link_id);
request.addParameter('name', TYPES.VarChar, data.name);
result = sqldb.runQuery(request, conn, res, '{}');
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', function(rowCount, more, rows){
console.log("The request procedure is done..");
_OnDone(empty, defaultContent, output);
console.log(rowCount, "rows returned");
// output.end();
});
console.log("Executing request");
executeRequest(request, connection);
}
function _OnDone(empty, defaultContent, 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;
错误信息和输出
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},{"corporate_statement_link_id":3,"name":"test","id":13},{"corporate_statement_link_id":3,"name":"test2","id":14},{"corporate_statement_link_id":3,"name":"test3","id":23},{"corporate_statement_link_id":3,"name":"test","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',
output: false,
length: undefined,
precision: undefined,
scale: undefined
}
],
parametersByName: {
corporate_statement_link_id: {
type: [Object],
name: 'corporate_statement_link_id',
value: 3,
output: false,
length: undefined,
precision: undefined,
scale: undefined
},
name: {
type: [Object],
name: 'name',
value: 'test4',
output: false,
length: undefined,
precision: undefined,
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'
}
我该如何解决，当找到标签时，它 return 绕过插入语句发送给客户端，但如果标签不存在，我想插入它然后发送标记给客户？
不是 运行 两个单独的查询，一个用于 SELECT，一个用于 INSERT，这实际上需要一个显式事务来确保一切始终一致，您可以执行一切只需一个查询，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'),
(1, 'tag3'),
(2, 'tag1'),
(2, 'tag4'),
(3, 'tag2'),
(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 table 并从那里进行查询：
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。您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。
此外，还要感谢@mauridb，他以一种很酷且更好的方式编写 SQL 查询，为我提供了很多帮助。
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', function(rowCount, more, 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，其他一切就位。然后，我只需要更新 router 以便它可以 return 将数据发送给客户端。
// 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, conn, parameters);
// using the query above, check if the tag already exists or not,
// and if
sqldb.runQuery(request, conn, (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);
}
});
第一次使用tedious.js，还不是很懂。我主要查看他们的文档 here.
下面是POST方法中的逻辑。
- 检查给定语句 id 的标签是否已经存在
- 如果标签存在，return消息给客户端
- 如果标签不存在，请将标签插入数据库。
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 ",data.name, "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', TYPES.Int, data.corporate_statement_link_id);
request.addParameter('name', TYPES.VarChar, data.name);
result = sqldb.runQuery(request, conn, res, '{}');
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', function(rowCount, more, rows){
console.log("The request procedure is done..");
_OnDone(empty, defaultContent, output);
console.log(rowCount, "rows returned");
// output.end();
});
console.log("Executing request");
executeRequest(request, connection);
}
function _OnDone(empty, defaultContent, 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;
错误信息和输出
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},{"corporate_statement_link_id":3,"name":"test","id":13},{"corporate_statement_link_id":3,"name":"test2","id":14},{"corporate_statement_link_id":3,"name":"test3","id":23},{"corporate_statement_link_id":3,"name":"test","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',
output: false,
length: undefined,
precision: undefined,
scale: undefined
}
],
parametersByName: {
corporate_statement_link_id: {
type: [Object],
name: 'corporate_statement_link_id',
value: 3,
output: false,
length: undefined,
precision: undefined,
scale: undefined
},
name: {
type: [Object],
name: 'name',
value: 'test4',
output: false,
length: undefined,
precision: undefined,
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'
}
我该如何解决，当找到标签时，它 return 绕过插入语句发送给客户端，但如果标签不存在，我想插入它然后发送标记给客户？
不是 运行 两个单独的查询，一个用于 SELECT，一个用于 INSERT，这实际上需要一个显式事务来确保一切始终一致，您可以执行一切只需一个查询，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'),
(1, 'tag3'),
(2, 'tag1'),
(2, 'tag4'),
(3, 'tag2'),
(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 table 并从那里进行查询：
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。您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。
此外，还要感谢@mauridb，他以一种很酷且更好的方式编写 SQL 查询，为我提供了很多帮助。
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', function(rowCount, more, 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，其他一切就位。然后，我只需要更新 router 以便它可以 return 将数据发送给客户端。
// 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, conn, parameters);
// using the query above, check if the tag already exists or not,
// and if
sqldb.runQuery(request, conn, (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);
}
});