在Kotlin公开的框架中处理子查询

dependencies {
    implementation "org.jetbrains.anko:anko-commons:0.10.8"
}

import org.jetbrains.anko.db.*

fun main() {
    val database = openOrCreateDatabase("mydatabase.db", null)
    
    database.use {
        createTable("Customers", true,
            "Id" to INTEGER + PRIMARY_KEY + AUTOINCREMENT,
            "Name" to TEXT,
            "Age" to INTEGER
        )
        
        createTable("Orders", true,
            "Id" to INTEGER + PRIMARY_KEY + AUTOINCREMENT,
            "CustomerId" to INTEGER,
            "Product" to TEXT,
            "Quantity" to INTEGER
        )
        
        insert("Customers",
            "Name" to "John",
            "Age" to 30
        )
        
        insert("Customers",
            "Name" to "Alice",
            "Age" to 25
        )
        
        insert("Orders",
            "CustomerId" to 1,
            "Product" to "Phone",
            "Quantity" to 2
        )
        
        insert("Orders",
            "CustomerId" to 2,
            "Product" to "Laptop",
            "Quantity" to 1
        )
        
        val result = select("Customers")
            .join("Orders", "Customers.Id = Orders.CustomerId")
            .whereArgs("Customers.Age > {age}", "age" to 20)
            .parseList(classParser<Customer>())
        
        for (customer in result) {
            println("${customer.name} bought ${customer.ordersCount} products")
        }
    }
}

data class Customer(val id: Int, val name: String) {
    var ordersCount: Int = 0
}