特殊SQL的执行

1、模糊查询

/**
* 测试模糊查询
* @param mohu
* @return
*/
List<User> testMohu(@Param("mohu") String mohu);

<!--List<User> testMohu(@Param("mohu") String mohu);-->
<select id="testMohu" resultType="User">
<!--select * from t_user where username like '%${mohu}%'-->
<!--select * from t_user where username like concat('%',#{mohu},'%')-->
select * from t_user where username like "%"#{mohu}"%"
</select>

2、批量删除

/**
* 批量删除
* @param ids
* @return
*/
int deleteMore(@Param("ids") String ids);

<!--int deleteMore(@Param("ids") String ids);-->
<delete id="deleteMore">
delete from t_user where id in (${ids})
</delete>

3、动态设置表名

/**
* 动态设置表名，查询所有的用户信息
* @param tableName
* @return
*/
List<User> getAllUser(@Param("tableName") String tableName);

<!--List<User> getAllUser(@Param("tableName") String tableName);-->
<select id="getAllUser" resultType="User">
select * from ${tableName}
</select>

4、添加功能获取自增的主键

t_clazz(clazz_id,clazz_name) t_student(student_id,student_name,clazz_id)

1、添加班级信息

2、获取新添加的班级的id

3、为班级分配学生，即将某学的班级id修改为新添加的班级的id

/**
* 添加用户信息
* @param user
* @return
* useGeneratedKeys：设置使用自增的主键
* keyProperty：因为增删改有统一的返回值是受影响的行数，因此只能将获取的自增的主键放在传输的参
数user对象的某个属性中
*/
int insertUser(User user);

<!--int insertUser(User user);-->
<insert id="insertUser" useGeneratedKeys="true" keyProperty="id">
insert into t_user values(null,#{username},#{password},#{age},#{sex})
</insert>

这里的意思是将新增的数据的ID放入实体类，

因为增删改有统一的返回值是受影响的行数，因此只能将获取的自增的主键放在传输的参数user对象的某个属性中

在这里就遇到了不能加引号的情况，所以只能使用${}

实例

public interface SQLMapper {

    /**
     * 根据用户名模糊查询用户信息
     */
    List<User> getUserByLike(@Param("username") String username);

    /**
     * 批量删除
     */
    int deleteMore(@Param("ids") String ids);

    /**
     * 查询指定表中的数据
     */
    List<User> getUserByTableName(@Param("tableName") String tableName);

    /**
     * 添加用户信息
     */
    void insertUser(User user);

}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.atguigu.mybatis.mapper.SQLMapper">

    <!--List<User> getUserByLike(@Param("username") String username);-->
    <select id="getUserByLike" resultType="User">
        <!--select * from t_user where username like '%${username}%'-->
        <!--select * from t_user where username like concat('%',#{username},'%')-->
        select * from t_user where username like "%"#{username}"%"
    </select>

    <!--int deleteMore(@Param("ids") String ids);-->
    <delete id="deleteMore">
        delete from t_user where id in (${ids})
    </delete>

    <!--List<User> getUserByTableName(@Param("tableName") String tableName);-->
    <select id="getUserByTableName" resultType="User">
        select * from ${tableName}
    </select>

    <!--
        void insertUser(User user);
        useGeneratedKeys:设置当前标签中的sql使用了自增的主键
        keyProperty:将自增的主键的值赋值给传输到映射文件中参数的某个属性
    -->
    <insert id="insertUser" useGeneratedKeys="true" keyProperty="id">
        insert into t_user values(null,#{username},#{password},#{age},#{sex},#{email})
    </insert>

</mapper>

public class SQLMapperTest {

    @Test
    public void testGetUserByLike(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        SQLMapper mapper = sqlSession.getMapper(SQLMapper.class);
        List<User> list = mapper.getUserByLike("a");
        System.out.println(list);
    }

    @Test
    public void testDeleteMore(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        SQLMapper mapper = sqlSession.getMapper(SQLMapper.class);
        int result = mapper.deleteMore("1,2,3");
        System.out.println(result);
    }

    @Test
    public void testGetUserByTableName(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        SQLMapper mapper = sqlSession.getMapper(SQLMapper.class);
        List<User> list = mapper.getUserByTableName("t_user");
        System.out.println(list);
    }

    @Test
    public void testInsertUser(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        SQLMapper mapper = sqlSession.getMapper(SQLMapper.class);
        User user = new User(null, "王五", "123", 23, "男", "[email protected]");
        mapper.insertUser(user);
        System.out.println(user);
    }

    @Test
    public void testJDBC() throws Exception {
        Class.forName("");
        Connection connection = DriverManager.getConnection("", "", "");
        PreparedStatement ps = connection.prepareStatement("insert", Statement.RETURN_GENERATED_KEYS);
        ps.executeUpdate();
        ResultSet resultSet = ps.getGeneratedKeys();
    }
}