一，新建.net core  web项目

二.  项目引入包:sqlSugarCore

三.创建两个表:user,   department

四. 新建model（不一定需要与table相同，使用[SugarTable("tableName")]进行model与table的绑定）

namespace SqlSugarTest01.Models
{
    [SugarTable("user")]
    public class UserModel
    {
        [SugarColumn(IsPrimaryKey =true,IsIdentity =true)]//如果是主键，此处必须指定，否则会引发InSingle(id)方法异常。
        public int id { get; set; }
        public string userName { get; set; }
        public string userPassword { get; set; }
        public int age { get; set; }
        public DateTime regTime { get; set; }
        public int departmentId { get; set; }
    }
}

 5.编写代码进行数据库操作，此处为了简便，我书写在HomeController中，开辟了一个方法区，在Index的return view()之前调用，以便进行调试。

（1）查询语句

public void SqlConnection()
        {
            //创建连接实体对象
            SqlSugarClient db = new SqlSugarClient(
                new ConnectionConfig()
                {
                    ConnectionString = "server=localhost;port=3307;uid=root;pwd=root;database=testsqlsugar",
                    DbType = DbType.MySql,//设置数据库类型
                    IsAutoCloseConnection = true,//自动释放数据库，如果存在事务，在事务结束之后释放。
                    InitKeyType = InitKeyType.Attribute//从实体特性中读取主键自增列信息
                });
            //aop监听sql，此段会在每一个"操作语句"执行时都进入....eg:getbyWhere这里会执行两次
            db.Aop.OnLogExecuting = (sql, pars) => {
                string sqlStempt = sql + "参数值：" + db.Utilities.SerializeObject(pars.ToDictionary(it => it.ParameterName, it => it.Value));
            };
            /*查询---单表*/
            var list = db.Queryable<UserModel>().ToList();//查询所有
            var getById = db.Queryable<UserModel>().InSingle(1);//根据主键查询（model中必须同步标识主键[SugarColumn(IsPrimaryKey =true,IsIdentity =true)]）
            var total = 0;
            var getbyWhere = db.Queryable<UserModel>().Where(it => it.age == 18).ToPageList(1, 2, ref total);//根据条件查询/分页.
            /*查询---多表*/
            var list0 = db.Queryable<UserModel, DepartmentModel>((user, dep) => new object[] {
                JoinType.Left,user.departmentId == dep.id}).Select((user, dep) => new { Id = user.id, depId = user.departmentId, name = user.userName }).ToList();
            //生成的sql: SELECT  `user`.`id` AS `Id` , `user`.`departmentId` AS `depId` , `user`.`userName` AS `name`  FROM `user` user Left JOIN `department` dep ON( `user`.`departmentId` = `dep`.`id` )
             //可用预先定义好的dto类自动填充select结果集，自动填充会比较依赖字段取名规则
            List<userDepDto> list1 = db.Queryable<UserModel, DepartmentModel>((user, dep) => new object[] { JoinType.Left, user.departmentId == dep.id }).Select<userDepDto>().ToList();
            List<userDepDto> list2 = db.Queryable<UserModel, DepartmentModel>((user, dep) => new object[] { JoinType.Left, user.departmentId == dep.id }).Select((user, dep) => new userDepDto { Id = dep.id, userName = user.userName, regTime = user.regTime, name = dep.name }).ToList();
            //三表查询，返回完整的三表对象。
            var list3 = db.Queryable<UserModel, DepartmentModel, UserInfoModel>((user, dep, userinfo) => new object[] { JoinType.Left, user.departmentId == dep.id, JoinType.Left, user.id == userinfo.UserId }).Where((user, dep, userinfo) => user.age == 18 || dep.id == 1 || userinfo.Sex == "男")
            .OrderBy((user) => user.id).OrderBy((user, dep) => dep.id, OrderByType.Desc).Select((user, dep, userInfo) => new { user = user, dep = dep, userInfo = userInfo }).ToList();
            //多表查询分页
            var list4 = db.Queryable<UserModel, DepartmentModel>((user, dep) => new object[] { JoinType.Left, user.departmentId == dep.id }).Select((user, dep) => new userDepDto { Id = user.id, userName = user.userName, regTime = user.regTime, name = dep.name }).ToPageList(2, 2);
            //两个Queryable的join
            var q1 = db.Queryable<UserModel, DepartmentModel>((user, dep) => new object[] { JoinType.Left, user.departmentId == dep.id }).Select((user,dep)=>new userDepDto() { Id=user.id,userName=user.userName,regTime=user.regTime,name=dep.name});
            var q2 = db.Queryable<UserModel>();
            // inner join
            var innerJoinList = db.Queryable(q1, q2, (j1, j2) => j1.Id == j2.id).Select((j1, j2) => j1).ToList();
            //left join
            var leftJoinList = db.Queryable(q1, q2, JoinType.Left, (j1, j2) => j1.Id == j2.id).Select((j1,j2)=>j1).ToList();
        }