https://medium.com/@shaibenshimol/nestjs-and-mysql-in-10-minutes-711e02ec1dab

ormconfig.json

  
{  
  "type": "mysql",  
  "host": "localhost",  
  "port": 3306,  
  "username": "root",  
  "password": "root",  
  "database": "my_nestjs_project",  
  "entities": ["src/**/**.entity{.ts,.js}"],  
  "synchronize": true,  
  "extra": { connectionLimit: 10, ... }  
}

Very Important !!

app.module

  
import { Module } from '@nestjs/common';  
import { UsersModule } from './users/users.module';  
import { TypeOrmModule } from '@nestjs/typeorm';  
  
@Module({  
  imports: [  
    TypeOrmModule.forRoot(),  
    UsersModule  
  ],  
})  
export class AppModule {}

=====nest command can use or not=====

  
nest g module users  
nest g service users  
nest g controller users  
nest g class users/user.entity

Use TypeORM Active Record
https://github.com/typeorm/typeorm/blob/master/docs/active-record-data-mapper.md

user.entity.ts

  
import {BaseEntity, Entity, PrimaryGeneratedColumn, Column} from "typeorm";  
  
@Entity()  
export class User extends BaseEntity {  
         
    @PrimaryGeneratedColumn()  
    id: number;  
      
    @Column()  
    firstName: string;  
      
    @Column()  
    lastName: string;  
      
    @Column()  
    isActive: boolean;  
  
    static findByName(firstName: string, lastName: string) {  
        return this.createQueryBuilder("user")  
            .where("user.firstName = :firstName", { firstName })  
            .andWhere("user.lastName = :lastName", { lastName })  
            .getMany();  
    }  
}

How to use

  
import { User } from './user.entity';  
  
const timber = await User.findByName("Timber", "Saw");

===== Use Other way ====

Users module

app.module.ts

  
import { Module } from '@nestjs/common';  
import { UsersModule } from './users/users.module';  
import { TypeOrmModule } from '@nestjs/typeorm';  
  
@Module({  
  imports: [  
    TypeOrmModule.forRoot(),  
    UsersModule  
  ],  
})  
export class AppModule {}

users.module.ts

  
import { Module } from '@nestjs/common';  
import { TypeOrmModule } from '@nestjs/typeorm';  
import { UsersService } from './users.service';  
import { UsersController } from './users.controller';  
import { User } from './user.entity';  
  
@Module({  
  imports: [TypeOrmModule.forFeature([User])],  
  providers: [UsersService],  
  controllers: [UsersController],  
})  
  
export class UsersModule { }

users.controller.ts

  
import { Controller, Post, Body, Get, Put, Delete,Param} from '@nestjs/common';  
import { UsersService } from './users.service';  
import { User } from './user.entity';  
  
@Controller('users')  
export class UsersController {  
  
    constructor(private service: UsersService) { }  
  
    @Get(':id')  
    get(@Param() params) {  
        return this.service.getUser(params.id);  
        //return timber = await User.findByName("Timber", "Saw");  
    }  
  
    @Post()  
    create(@Body() user: User) {  
        return this.service.createUser(user);  
    }  
  
    @Put()  
    update(@Body() user: User) {  
        return this.service.updateUser(user);  
    }  
  
    @Delete(':id')  
    deleteUser(@Param() params) {  
        return this.service.deleteUser(params.id);  
    }  
}

users.service.ts This file maybe don’t need because use Active Record.

  
import { Injectable, Inject } from '@nestjs/common';  
import { InjectRepository } from '@nestjs/typeorm';  
import { Repository } from 'typeorm';  
import { User } from './user-entity';  
  
@Injectable()  
export class UsersService {  
  
    constructor(@InjectRepository(User) private usersRepository: Repository) { }  
  
    async getUsers(user: User): Promise {  
        return await this.usersRepository.find();  
    }  
  
    async getUser(_id: number): Promise {  
        return await this.usersRepository.find({  
            select: ["fullName", "birthday", "isActive"],  
            where: [{ "id": _id }]  
        });  
    }  
  
    async updateUser(user: User) {  
        this.usersRepository.save(user)  
    }  
  
    async deleteUser(user: User) {  
        this.usersRepository.delete(user);  
    }  
}

https://blog.entrostat.com/setting-up-a-database-module-in-nest-js/