salix/modules/travel/back/methods/travel/getAverageDays.js

const ParameterizedSQL = require('loopback-connector').ParameterizedSQL;
module.exports = Self => {
    Self.remoteMethod('getAverageDays', {
        description: 'Returns the average days duration and the two warehouses of the travel.',
        accessType: 'READ',
        accepts: [{
            arg: 'agencyModeFk',
            type: 'number',
            required: true
        }],
        returns: {
            type: 'object',
            root: true
        },
        http: {
            path: `/getAverageDays`,
            verb: 'GET'
        }
    });

    Self.getAverageDays = async agencyModeFk => {
        const conn = Self.dataSource.connector;
        let stmts = [];

        stmts.push('DROP TEMPORARY TABLE IF EXISTS tmp.travel');

        stmt = new ParameterizedSQL(`
            CREATE TEMPORARY TABLE tmp.travel (
                SELECT 
                    t.id, 
                    t.warehouseInFk, 
                    t.warehouseOutFk, 
                    t.landed, 
                    t.shipped,
                    t.agencyModeFk
                FROM travel t
                    WHERE t.agencyModeFk = ? LIMIT 50)`, [agencyModeFk]);
        stmts.push(stmt);

        stmt = new ParameterizedSQL(`
            SELECT 
                t.id, 
                t.warehouseInFk, 
                t.warehouseOutFk, 
                    (SELECT ROUND(AVG(DATEDIFF(t.landed, t.shipped )))
                    FROM tmp.travel t 
                    WHERE t.agencyModeFk 
                        ORDER BY id DESC LIMIT 50) AS dayDuration
            FROM tmp.travel t
            WHERE t.agencyModeFk 
                ORDER BY t.id DESC LIMIT 1`);

        const avgDaysIndex = stmts.push(stmt) - 1;

        stmts.push(
            `DROP TEMPORARY TABLE 
                tmp.travel`);

        const sql = ParameterizedSQL.join(stmts, ';');
        const result = await conn.executeStmt(sql);

        const [avgDays] = result[avgDaysIndex];

        return avgDays;
    };
};