Sequelize - 在不同条件下两次计算相同的关联答案

【问题标题】：Sequelize - Counting the same association twice under different conditionsSequelize - 在不同条件下两次计算相同的关联
【发布时间】：2018-09-20 18:57:42
【问题描述】：

我正在尝试根据不同的参数在关联表中获取两个记录计数：

// Models
var Customer = sequelize.define('Customer', {
    name: DataTypes.STRING,
});
var Invoice = sequelize.define('Invoice', {
    invoiceRef: DataTypes.STRING,
    status: {
        type: DataTypes.ENUM,
        values: ['UNPAID', 'PAID'],
        defaultValue: 'UNPAID'
    },
    isArchived: {
        type: DataTypes.BOOLEAN,
        defaultValue: false
    },
});
Invoice.associate = function(models) {
    Invoice.belongsTo(models.Customer);
}
Customer.associate = function (models) {
    Customer.hasMany(models.Invoice);
}


// Query
Customer.findAll({
    attributes: {
        include: [
            [models.Sequelize.fn("COUNT", models.Sequelize.fn("DISTINCT", models.Sequelize.col("Invoices.id"))), "totalInvoices"],
            [models.Sequelize.fn("COUNT", models.Sequelize.fn("DISTINCT", models.Sequelize.col("UnpaidInvoices.id"))), "unpaidInvoices"]
        ]
    },
    include: [
        {
            model: models.Invoice,
            where: { isArchived: false },
            attributes: [],
            required: false
        },
        {
            model: models.Invoice,
            where: { isArchived: false, status: 'UNPAID' },
            attributes: [],
            required: false
        },
    ],
    group: ['Customer.id']
})

问题在于，当多次包含同一个关联表时，Sequelize 会为 SQL 查询中表的两个实例分配相同的名称：

左外连接 Invoices AS Invoices ON Customer.id = Invoices.CustomerId AND Invoices.isArchived = 0
左外连接 Invoices AS Invoices ON Customer.id = Invoices.CustomerId AND Invoices.isArchived = 0 AND Invoices.'@UNPAID'365 p>

有没有办法为查询中的连接表指定不同的名称？例如：

左外连接 Invoices AS Invoices ON Customer.id = Invoices.CustomerId AND Invoices.isArchived = 0
左外连接Invoices AS UnpaidInvoices ON Customer.id = Invoices.CustomerId AND Invoices.isArchived = 0 AND Invoices@. @ = '未付'

【问题讨论】：

标签： sql count associations sequelize.js

【解决方案1】：

我通常只加入一次，然后将 CASE 语句与 SUM 一起使用，而不是使用 COUNT - 行都已加入，这就是为什么你会得到相同的结果。

attributes: {
  include: [
    // count paid using case/sum via `status` != 'UNPAID'
    [ sequelize.fn('sum', sequelize.literal("CASE WHEN (`Invoices`.`status` != 'UNPAID' THEN 1 ELSE 0 END")), 'paid_count' ],
    // count unpaid using case/sum via `status` = 'UNPAID'
    [ sequelize.fn('sum', sequelize.literal("CASE WHEN (`Invoices`.`status` = 'UNPAID' THEN 1 ELSE 0 END")), 'unpaid_count' ],
  ],
  // ...
},

【讨论】：