Node.js MySQL 从表中选取

从表中选取

要从 MySQL 中的表中选择数据，请使用 "SELECT" 语句。

实例

从 "customers" 表中选择所有记录，并显示结果对象:

var mysql = require('mysql');
var con = mysql.createConnection({
 host: "localhost",
 user: "yourusername",
 password: "yourpassword",
 database: "mydb"
});
con.connect(function(err) {
 if (err) throw err;
  con.query("<strong>SELECT * FROM customers</strong>", function (err, result, fields) {
   if (err) throw err;
  console.log(result);
 });
});

将上述代码保存在名为 "demo_db_select.js" 的文件中，然后运行该文件:

运行 "demo_db_select.js"

结果如下:

[
 { id: 1, name: 'John', address: 'Highway 71'},
 { id:  2, name: 'Peter', address: 'Lowstreet 4'},
 { id: 3, name: 'Amy',  address: 'Apple st 652'},
 { id: 4, name: 'Hannah', address:  'Mountain 21'},
 { id: 5, name: 'Michael', address: 'Valley 345'},
 { id: 6, name: 'Sandy', address: 'Ocean blvd 2'},
 { id: 7,  name: 'Betty', address: 'Green Grass 1'},
 { id: 8, name: 'Richard',  address: 'Sky st 331'},
 { id: 9, name: 'Susan', address: 'One way  98'},
 { id: 10, name: 'Vicky', address: 'Yellow Garden 2'},
 { id: 11, name: 'Ben', address: 'Park Lane 38'},
 { id: 12, name: 'William',  address: 'Central st 954'},
 { id: 13, name: 'Chuck', address:  'Main Road 989'},
 { id: 14, name: 'Viola', address: 'Sideway  1633'}
]

选择列

要仅选择表中的某些列，请使用 "SELECT" 语句，后跟列名。

实例

从 "customers" 表中选择名称和地址，并显示返回对象:

var mysql = require('mysql');
var con = mysql.createConnection({
 host: "localhost",
 user: "yourusername",
 password: "yourpassword",
 database: "mydb"
});
con.connect(function(err) {
 if (err) throw err;
  con.query("<strong>SELECT name, address FROM customers</strong>", function (err, result, fields) {
   if (err) throw err;
  console.log(result);
 });
});

将上述代码保存在名为 "demo_db_select2.js" 的文件中，然后运行该文件:

运行 "demo_db_select2.js"

结果如下:

[
 { name: 'John', address: 'Highway 71'},
 { name: 'Peter', address: 'Lowstreet 4'},
 { name: 'Amy',  address: 'Apple st 652'},
 { name: 'Hannah', address:  'Mountain 21'},
 { name: 'Michael', address: 'Valley 345'},
 { name: 'Sandy', address: 'Ocean blvd 2'},
 { name: 'Betty', address: 'Green Grass 1'},
 { name: 'Richard',  address: 'Sky st 331'},
 { name: 'Susan', address: 'One way  98'},
 { name: 'Vicky', address: 'Yellow Garden 2'},
 { name: 'Ben', address: 'Park Lane 38'},
 { name: 'William',  address: 'Central st 954'},
 { name: 'Chuck', address:  'Main Road 989'},
 { name: 'Viola', address: 'Sideway  1633'}
]

结果对象

从上面示例的结果可以看出，result 结果对象是一个数组，包含作为对象的每一行。

要返回例如第三条记录的地址，只需参考第三个数组对象的 address 属性:

实例

返回第三条记录的地址:

结果如下:

 Apple st 652

字段对象

回调函数的第三个参数是一个数组，其中包含有关结果中每个字段的信息。

实例

从 "customers" 表中选择所有记录，并显示 字段 对象:

var mysql = require('mysql');
 var con = mysql.createConnection({
  host: "localhost",
 user: "yourusername",
  password: "yourpassword",
 database: "mydb"
});
con.connect(function(err) {
 if (err) throw err;
  con.query("SELECT name, address FROM customers", function (err,  result, <strong>fields</strong>) {
   if (err) throw err;
  console.log(<strong>fields</strong>);
 });
 });

将上述代码保存在名为 "demo_db_select_fields.js" 的文件中，然后运行该文件:

运行 "demo_db_select_fields.js"

结果如下:

[
 {
  catalog: 'def',
  db:  'mydb',
  table: 'customers',
  orgTable: 'customers',
  name: 'name',
  orgName: 'name',
  charsetNr: 33,
  length: 765,
  type: 253,
  flags: 0,
  decimals: 0,
  default: undefined,
  zeroFill: false,
  protocol41: true
 },
 {
  catalog: 'def',
  db: 'mydb',
  table: 'customers',
  orgTable: 'customers',
  name: 'address',
  orgName: 'address',
  charsetNr: 33,
  length: 765,
  type:  253,
  flags: 0,
  decimals: 0,
  default: undefined,
  zeroFill: false,
  protocol41: true
 }
]

从上面示例的结果可以看出，fields 对象是一个数组，其中包含每个字段作为对象的信息。

要返回第二个字段的名称，只需参考第二个数组项的 name 属性:

实例

返回第二个字段的名称:

结果如下:

 address