一、执行安装mysql命令：npm install mysql -S

const express = require('express');
const {buildSchema} = require('graphql');
const {graphqlHTTP} = require('express-graphql');
const mysql = require('mysql');

// http://www.npmjs.com/package/mysql
var pool  = mysql.createPool({
  connectionLimit : 10,
  host            : 'localhost',
  user            : 'root',
  password        : '',
  database        : 'my_db'
});

// 定义Schema,  查询方法和返回值类型
const schema = buildSchema(`
    input AccountInput {
        name: String
        age: Int
        sex: String
        department: String
    }

    type Account {
        name: String
        age: Int
        sex: String
        department: String
    }

    type Mutation {
        createAccount(input: AccountInput): Account
        updateAccount(id: ID!, input: AccountInput): Account
        deleteAccount(id: ID!): Boolean
    }

    type Query {
        accounts: [Account]
    }
`)

//定义查询对应的处理器
const root = {

   //添加操作
   createAccount({input}) {
      const data = {
        name: input.name,
        age: input.age,
        sex: input.sex,
        department: input.department
      };
      return new promise((resolve, reject) => {
        pool.query('insert into account set ?', data, (err) => {
          if (err) {
            console.log('出错了' + err.message);
            return;
          }
          resolve(data);
        })
      })
    },
    
    // 更新操作
    updateAccount({id, input}) {
        const data = input;
        return new promise((resolve, reject) => {
           pool.query('update account set ? where name = ?', [data, id], (err) => {
              if (err) {
                 console.log('出错了' + err.message);
                 return;
              }
              resolve(data);
           })
        })
    },
    
    // 查询操作
    accounts() {
        return new promise((resolve, reject) => {
          pool.query('select name, age, sex, department from account', (err, results) => {
             if (err) {
                console.log('出错了' + err.message);
                return;
             }
             const arr = [];
             for (let i = 0; i < results.length; i++) {
               arr.push({
                  name: results[i].name,
                  age: results[i].age,
                  sex: results[i].sex,
                  department: results[i].department
               })
             }
             resolve(arr);
          })
        })
    },
    
    //删除操作
    deleteAccount({id}) {
        return new promise((resolve, reject) => {
           pool.query('delete from account where name = ?', [id], (err) => {
                if (err) {
                    console.log('出错了' + err.message);
                    reject(false);
                    return;
                }
                resolve(true);
           })
        })  
    }
}

const app = express();

app.use('/graphql', graphqlHTTP({
    schema: schema,
    rootValue: root,
    graphiql: true
}))


app.listen(3000);