Having Clause in GORM

Install Libraries

Make sure Git is installed on your machine and in your system’s PATH. Install the package to your $GOPATH with the go tool from shell:

$ go get github.com/go-sql-driver/mysql
$ go get -u github.com/jinzhu/gorm

Create Database

Create a database with the name is learngorm. This database have 1 tables: Product table.

--
-- Table structure for table `product`
--

CREATE TABLE `product` (
  `id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT,
  `name` varchar(250) NOT NULL,
  `price` double NOT NULL,
  `quantity` int(11) NOT NULL,
  `status` tinyint(1) NOT NULL,
  `created` date DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

--
-- Dumping data for table `product`
--

INSERT INTO `product` (`name`, `price`, `quantity`, `status`, `created`) VALUES
('Tivi 1', 4, 2, 1, '2019-07-10'),
('Tivi 2', 7, 22, 0, '2019-11-08'),
('Mobile 1', 11, 7, 1, '2019-07-11'),
('Mobile 2', 26, 8, 1, '2018-05-04'),
('Computer 1', 8, 2, 0, '2018-07-26');

Structure of Product Table

Data of Product Table

Create Entities

Create new folder named src. In src folder, create new folder named entities. In entities folder, create new entities as below:

Product Entity

In entities folder, create new go file named product.entity.go as below:

package entities

import (
	"fmt"
	"time"
)

type Product struct {
	Id       int `gorm:"primary_key, AUTO_INCREMENT"`
	Name     string
	Price    float64
	Quantity int
	Status   bool
	Created  time.Time
}

func (product *Product) TableName() string {
	return "product"
}

func (product Product) ToString() string {
	return fmt.Sprintf("id: %d\nname: %s\nprice: %0.1f\nquantity: %d\nstatus: %t\ncreated: %s", product.Id, product.Name, product.Price, product.Quantity, product.Status, product.Created.Format("02/01/2006"))
}

ProductGroup Entity

In entities folder, create new go file named productgroup.entity.go as below:

package entities

type ProductGroup struct {
	Status  bool
	Result1 int     // Count Product
	Result2 int     // Sum Quantities
	Result3 float64 // min price
	Result4 float64 // max price
	Result5 float64 // avg price
}

Create Config

In src folder, create new folder named config. In this folder, create new file named config.go, this file is used to connect mysql database:

package config

import (
	"github.com/jinzhu/gorm"
	_ "github.com/jinzhu/gorm/dialects/mysql"
)

func GetDB() (*gorm.DB, error) {
	dbDriver := "mysql"
	dbName := "learngorm"
	dbUser := "root"
	dbPassword := "123456"
	db, err := gorm.Open(dbDriver, dbUser+":"+dbPassword+"@/"+dbName+"?charset=utf8&parseTime=True")
	if err != nil {
		return nil, err
	}
	return db, nil
}

Create Model

In src folder, create new folder named models. In models folder, create new file named product.model.go. This file contains methods to interact with the database.

package models

import (
	"config"
	"entities"
)

type ProductModel struct {
}

func (productModel ProductModel) Having() ([]entities.ProductGroup, error) {
	db, err := config.GetDB()
	if err != nil {
		return nil, err
	} else {
		var productGroups []entities.ProductGroup
		db.Table("product")
			.Select("status, count(id) as result1, sum(quantity) as result2, min(price) as result3, max(price) as result4, avg(price) as result5")
			.Group("status")
			.Having("count(id) > ?", 2)
			.Scan(&productGroups)
		return productGroups, nil
	}
}

Structure of Project

Run Application

In src folder, create new file named main.go as below and use go run main.go command to run program:

package main

import (
	"fmt"
	"models"
)

func main() {
	var productModel models.ProductModel
	productGroups, _ := productModel.Having()
	for _, productGroup := range productGroups {
		fmt.Println("status: ", productGroup.Status)
		fmt.Println("count product: ", productGroup.Result1)
		fmt.Println("sum quantities: ", productGroup.Result2)
		fmt.Println("min price: ", productGroup.Result3)
		fmt.Println("max price: ", productGroup.Result4)
		fmt.Println("avg price: ", productGroup.Result5)
		fmt.Println("--------------------")
	}
}

Output

status:  true
count product:  3
sum quantities:  17
min price:  4
max price:  26
avg price:  13.666666666666666
--------------------