`JavaScript
// Utility
import stringify from "json-stringify-pretty-compact";

// Co-dependency
import MySQL from "mysql2/promise";

// Library
import ZQL from "../ZQL.js";

// Generic model that suppresses values used for population
class Model {

constructor( obj ) {

Object.defineProperties( this, {
_table_source: { writable: true },
_table_sources: { writable: true }
} );

Object.assign( this, obj );

}

}

// Person model
class Person extends Model {}

// Friend model; is a relationship, thus we only return the related object (or its id)
class Friend extends Model {

toJSON() {

if ( this.target ) return this.target;
return this.targetId;

}

}

// Lookups
const models = { person: Person, friend: Friend };

( async () => {

// We still use a normal MySQL connection
const mysql = await MySQL.createConnection( {
host: "localhost",
multipleStatements: true, // Multiple statements are a must!
user: "test",
database: "test"
} );

// Query function used by ZQL
const query = ( ...args ) => mysql.query( ...args );

// Optional mapping between MySQL's TextRow and our models; note the rows are just that, without populated fields
const replacer = ( row, table ) => {

if ( models[ table.name ] ) return new models table.name ;
console.warn( "Unknown model", table );
return new Model( row );

};

// When populating, we don't want to overwrite values; note relationship populations generally don't have an Id or corresponding field to overwrite
const populater = ( doc, field, value ) => {

if ( field.endsWith( "Id" ) ) return doc[ field.slice( 0, - 2 ) ] = value;
if (doc[field]) throw new Error(Tried to populate over existing field '${field}' on '${doc.constructor.name}')
return doc[ field ] = value;

};

// Our ZQL, auto-generating the spec
const zql = new ZQL( { query/, format/, autogen: true, database: "test", replacer, populater } );

// Make sure the spec is ready
await zql.ready;

} )().catch( err => ( console.error( err ), process.exit( 1 ) ) );
`