Node.js Getting Started Tutorial Part VI (connection to use MySql)

MySql connection

MySql installation modules:

 npm install mysql 

Create a connection:

. 1 const = mysql the require ( 'mysql' )
 2  
. 3  // connect mysql server 
. 4 const = Connection mysql.createConnection ({
 . 5    Host: '127.0.0.1' ,
 . 6    User: 'the root', // the user name to access the database 
7    password: '123456', // database access password 
. 8    port: '3306', // database port number 
. 9    database: 'XXX', // name of the database 
10  })
 11  // execute the SQL 
12 is connection.query (SQL, function (ERR, Result) {
 13 is    ERR //Error message 
14    the Result // result 
15  })
 16  // destroy a connection | Because JS is asynchronous, so the current code before executing the SQL connections were destroyed 
17 connection.destroy ()

Mysql create a connection createConnection, Each time a new connection is connection.query will cause a great waste of resources, reduce performance.

Connection pooling is another method of performing, it created a number of one-time connection, and then according to the client's queries, automatic distribution, reuse, manage these connections.

. 1 const = MySQL the require ( 'MySQL' )
 2  
. 3  // Create a connection pool 
. 4 const the pool = mysql.createPool ({
 . 5    Host: '127.0.0.1' ,
 . 6    User: 'the root', // the user name to access the database 
7    password: '123456', // database access password 
. 8    port: '3306', // database port number 
. 9    database: 'XXX', // name of the database 
10  })
 . 11  
12 is const DB = {  
 13 is     sqlQuery (SQL, values ) {
 14      return  new new Promise ((Resolve, Reject) => {
15       pool.getConnection((err, connection) => {
16         if (err) {
17           reject(err)
18         } else {
19           if (values) {
20             connection.query(sql, values, (err, rows) => {
21               if (err) {
22                 reject(err)
23               } else {
24                 resolve(rows)
25               }
26               connection.release()
27             });
28           } else {
29             connection.query(sql, (err, rows) => {
30               if (err) {
31                 reject(err)
32               } else {
33                 resolve(rows)
34               }
35               connection.release()
36             });
37           }
38         }
39       })
40     })
41   }
42 }

? MySql query variable with a number as a placeholder (to prevent SQL injection):

1 var query = 'UPDATE users SET foo = ?, bar = ?, baz = ? WHERE id = ?',
2     value = ['a', 'b', 'c', userId];
3 connection.query(query, value, (error, results, fields) => { /* ... */ });

The first parameter is a query string, the query is sql statement contains placeholders.

The second parameter value is an array containing all values ​​placeholder.

 

Identifiers (database, table, column names) with two numbers as a placeholder (ie ??), in addition to the identifier name can be passed as query variables together into a list of values?:

1 var query = 'UPDATE ?? SET foo = ?, bar = ?, baz = ? WHERE id = ?',
2     value = ['users', 'a', 'b', 'c', userId];
3 connection.query(query, value, (error, results, fields) => { /* ... */ });