如何使用别名选择列

Question

如何执行这样的 sql 查询？

SELECT column_name AS alias_name FROM table_name;

示例：我希望将“first”列选为“firstname”

Table.findAll({
      attributes: [id,"first"]
    })
    .then(function(posts) {
        res.json(posts);
    })

Answer 1

您需要使用row.get('newname') 访问以attributes 为别名的列

出于某种原因，仅使用 row.newname 或 row.oldname 不会像处理非别名名称那样工作：

• https://github.com/sequelize/sequelize/issues/10592

• https://sequelize.org/v5/manual/models-usage.html 记录它：

  Project.findOne({
    where: {title: 'aProject'},
    attributes: ['id', ['name', 'title']]
  }).then(project => {
    // project will be the first entry of the Projects table with the title
    // 'aProject' || null
    // project.get('title') will contain the name of the project
  })
  

  但https://sequelize.org/master/class/lib/model.js~Model.html 并没有提及，这令人困惑：

  instance.field
  // is the same as
  instance.get('field')
  

相关：Sequelize cannot access alias. Alias is undefined

最小的可运行示例：

const assert = require('assert');
const path = require('path');
const { Sequelize, DataTypes, Op } = require('sequelize');
const sequelize = new Sequelize({
  dialect: 'sqlite',
  storage: path.basename(__filename) + '.sqlite',
});
(async () => {
const Int = sequelize.define('Int', {
  value: {
    type: DataTypes.INTEGER,
  },
  name: {
    type: DataTypes.STRING,
  },
}, {});
await Int.sync({force: true})
await Int.create({value: 2, name: 'two'});
let row;
row = await Int.findOne({
  where: { value: 2 },
  attributes: [ 'id', [ 'value', 'newvalue' ] ],
});
assert.strictEqual(row.id, 1);
assert.strictEqual(row.value, undefined);
assert.strictEqual(row.newvalue, undefined);
assert.strictEqual(row.get('newvalue'), 2);
await sequelize.close();
})();

生成的查询完全符合我们当时的要求：

SELECT `id`, `value` AS `newvalue` FROM `Ints` AS `Int`
  WHERE `Int`.`value` = 2 LIMIT 1;

在 sequelize 6.5.1、sqlite3 5.0.2 上测试。

Answer 2

Sequelize 也支持直接在模型定义上定义列名。

Sequelize Docs 他们在列定义中提到了field 属性。

例如：（取自文档本身）

const { Model, DataTypes, Deferrable } = require("sequelize");

class Foo extends Model { }
Foo.init({
    // You can specify a custom column name via the 'field' attribute:
    fieldWithUnderscores: {
        type: DataTypes.STRING, 
        field: 'field_with_underscores'
    },
}, {
    sequelize,
    modelName: 'foo'
});

感谢this answer

Answer 3

Table.findAll({
  attributes: ['id', ['first', 'firstName']] //id, first AS firstName
})
.then(function(posts) {
  res.json(posts);
});