<!--int insertUser();-->
<insert id="insertUser">
    insert into t_user values(null,'admin','123456',23,'男')
</insert>

<!--int deleteUser();-->
<delete id="deleteUser">
    delete from t_user where id = 1
</delete>

<!--int updateUser();-->
<update id="updateUser">
    update t_user set username='ybc',password='123' where id = 6
</update>

<!--User getUserById();-->
<select id="getUserById" resultType="com.ssm.mybatis.bean.User">
    select * from t_user where id = 2
</select>

<!--List<User> getUserList();-->
<select id="getUserList" resultType="com.ssm.mybatis.bean.User">
    select * from t_user
</select>

    <!--User getUserByUsername(String username);-->
    <select id="getUserByUsername" resultType="User">
        <!--select * from t_user where username = '${username}'-->
        select * from t_user where username = #{username}
    </select>

    <!--User checkLogin(String username, String password);-->
    <select id="checkLogin" resultType="User">
        <!--select * from t_user where username = '${arg0}' and password = '${arg1}'-->
        <!--select * from t_user where username = #{param1} and password = #{param2}-->
        select * from t_user where username = #{arg0} and password = #{arg1}
 
    </select>

    <!--User checkLoginByMap(Map<String ,Object> map);-->
    <select id="checkLoginByMap" resultType="User">
        <!--select * from t_user where username = '${username}' and password = '${password}'-->
        select * from t_user where username = #{username} and password = #{password}
    </select>

    <!--void insertUser(User user);-->
    <insert id="insertUser" >
        insert into t_user values(null,#{username},#{password},#{age},#{gender},#{email})
    </insert>

    <!--User checkLoginByParam(@Param("username") String username, @Param("password") String password);-->
    <select id="checkLoginByParam" resultType="User">
        <!--select * from t_user where username = '${username}' and password = '${password}'-->
        select * from t_user where username = #{username} and password = #{password}
    </select>

package com.ssm.mybatis.mapper;
 
import com.ssm.mybatis.pojo.User;
import org.apache.ibatis.annotations.Param;
 
import java.util.List;
 
/**
 * Author：wy
 * Date：2023/3/18
 */
 
public interface SelectMapper {
    /**
     * 根據(jù)用戶(hù)id查詢(xún)用戶(hù)信息
     * @param id
     * @return
     */
    User getUserById(@Param("id") int id);
}

<!--User getUserById(@Param("id") int id);-->
<select id="getUserById" resultType="User">
    select * from t_user where id = #{id}
</select>

    @Test
    public void testGetUserById() {
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);
 
        User user = mapper.getUserById(1);
        System.out.println(user);
    }

    /**
     * 查詢(xún)所有用戶(hù)信息
     * @return
     */
    List<User> getUserList();

    <!--List<User> getUserList();-->
    <select id="getUserList" resultType="User">
        select * from t_user
    </select>

    @Test
    public void testGetUserList() {
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);
 
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
    }

    /**
     * 查詢(xún)用戶(hù)的總記錄數(shù)
     * @return
     */
    Integer getCount();

     <!--Integer getCount();-->
    <!--
        在MyBatis中，對(duì)于Java中常用的類(lèi)型都設(shè)置了類(lèi)型別名
        例如： Integer: int, integer
        例如： int: _int, _integer
        例如： Map: map
              List: list
    -->
    <select id="getCount" resultType="Integer">
        select count(*) from t_user
    </select>

    @Test
    public void testGetCount() {
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);
 
        Integer count = mapper.getCount();
        System.out.println("用戶(hù)總數(shù)=" + count);
    }

    /**
     * 根據(jù)用戶(hù)id查詢(xún)用戶(hù)信息為map集合
     * @param id
     * @return
     */
    Map<String, Object> getUserByIdToMap(@Param("id") Integer id);

    <!--Map<String, Object> getUserByIdToMap(@Param("id") int id);-->
    <select id="getUserByIdToMap" resultType="map">
        select * from t_user where id = #{id}
    </select>

    @Test
    public void testGetUserByIdToMap() {
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);
 
        Map<String, Object> map = mapper.getUserByIdToMap(1);
        System.out.println(map);
        //結(jié)果：{password=123456, gender=男, id=1, age=21, email=123456@qq.com, username=張三}
    }

    /**
     * 查詢(xún)所有用戶(hù)信息為map集合
     * @return
     * 將表中的數(shù)據(jù)以map集合的方式查詢(xún)，一條數(shù)據(jù)對(duì)應(yīng)一個(gè)map；若有多條數(shù)據(jù)，就會(huì)產(chǎn)生多個(gè)map集合
       此時(shí)可以將這些map放在一個(gè)list集合中獲取
     */
    @MapKey("id")
    List<Map<String, Object>> getAllUserToMap();

    <!--Map<String, Object> getAllUserToMap();-->
    <select id="getAllUserToMap" resultType="map">
        select * from t_user
    </select>

    @Test
    public void testGetAllUserToMap() {
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);
 
        List<Map<String, Object>> allUserToMap = mapper.getAllUserToMap();
 
        for (Map<String, Object> map : allUserToMap) {
            System.out.println(map);
        }
    }

    /**
     * 查詢(xún)所有用戶(hù)信息為map集合
     * @return
     * 可以將每條數(shù)據(jù)轉(zhuǎn)換的map集合放在一個(gè)大的map中，
     * 但是必須要通過(guò)@Mapkey注解將查詢(xún)的某個(gè)字段的值作為大的map的鍵
     */
    @MapKey("id")
    Map<String, Object> getAllUserToMap();

    <!--Map<String, Object> getAllUserToMap();-->
    <select id="getAllUserToMap" resultType="map">
        select * from t_user
    </select>

    @Test
    public void testGetAllUserToMap() {
        SqlSession sqlSession = SqlSessionUtil.getSqlSession();
        SelectMapper mapper = sqlSession.getMapper(SelectMapper.class);
 
        Map<String, Object> map = mapper.getAllUserToMap();
        System.out.println(map);
        //{ 
        // 1={password=123456, gender=男, id=1, age=21, email=123456@qq.com, username=張三}, 
        // 2={password=123456, gender=女, id=2, age=19, email=123456@qq.com, username=老六} 
        // }
    }