- DML（data manipulation language）： 它们是SELECT、UPDATE、INSERT、DELETE，就象它的名字一样，这4条命令是用来对数据库里的数据进行操作的语言
- DDL（data definition language）： DDL比DML要多，主要的命令有CREATE、ALTER、DROP等，DDL主要是用在定义或改变表（TABLE）的结构，数据类型，表之间的链接和约束等初始化工作上，他们大多在建立表时使用
- DCL（Data Control Language）： 是数据库控制功能。是用来设置或更改数据库用户或角色权限的语句，包括（grant,deny,revoke等）语句。在默认状态下，只有sysadmin,dbcreator,db_owner或db_securityadmin等人员才有权力执行DCL
Mysql常用命令
- mysql 初始化时修改密码
alert user user() identified by "密码"；SqlMapConfig.xml
```xml <?xml version=”1.0” encoding=”UTF-8”?> <!DOCTYPE configuration PUBLIC “-//mybatis.org//DTD Config 3.0//EN” “http://mybatis.org/dtd/mybatis-3-config.dtd”>
### jdbcConfig.properties
```properties
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/eesy_mybatis
jdbc.username=root
jdbc.password=1234
映射文件XxxDao.xml
<?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.xxx.dao.IUserDao">
<!-- 查询所有 -->
<select id="findAll" resultType="com.xxx.domain.User">
select * from user;
</select>
<!-- 保存用户 -->
<insert id="saveUser" parameterType="com.xxx.domain.User">
<!-- 配置插入操作后，获取插入数据的id -->
<selectKey keyProperty="id" keyColumn="id" resultType="int" order="AFTER">
select last_insert_id();
</selectKey>
insert into user(username,address,sex,birthday)values(#{username},#{address},#{sex},#{birthday});
</insert>
<!-- 更新用户 -->
<update id="updateUser" parameterType="com.xxx.domain.User">
update user set username=#{username},address=#{address},sex=#{sex},birthday=#{birthday} where id=#{id}
</update>
<!-- 删除用户-->
<delete id="deleteUser" parameterType="java.lang.Integer">
delete from user where id = #{uid}
</delete>
<!-- 根据id查询用户 -->
<select id="findById" parameterType="INT" resultType="com.xxx.domain.User">
select * from user where id = #{uid}
</select>
<!-- 根据名称模糊查询 -->
<select id="findByName" parameterType="string" resultType="com.xxx.domain.User">
select * from user where username like #{name}
</select>
<!-- 获取用户的总记录条数 -->
<select id="findTotal" resultType="int">
select count(id) from user;
</select>
</mapper>
mybatis入门案例
- mybatis-config.xml ```xml
<?xml version=”1.0” encoding=”UTF-8”?> <!DOCTYPE configuration PUBLIC “-//mybatis.org//DTD Config 3.0//EN” “http://mybatis.org/dtd/mybatis-3-config.dtd”>
- xxMapper.xml
```xml
<?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">
public class MybatisTest {
/**
* 入门案例
* @param args
*/
public static void main(String[] args)throws Exception {
//1.读取配置文件
InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
//2.创建SqlSessionFactory工厂
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
SqlSessionFactory factory = builder.build(in);
//3.使用工厂生产SqlSession对象
SqlSession session = factory.openSession();
//4.使用SqlSession创建Dao接口的代理对象
IUserDao userDao = session.getMapper(IUserDao.class);
//5.使用代理对象执行方法
List<User> users = userDao.findAll();
for(User user : users){
System.out.println(user);
}
//6.释放资源
session.close();
in.close();
}
}
mybatis复杂条件查询
<select id="findUserByCondition" resultMap="userMap" parameterType="user">
select * from user
<where>
<if test="userName != null">
and username = #{username}
</if>
<if test="userSex != null">
and sex = #{sex}
</if>
</where>
</select>
<!-- 根据queryvo中的Id集合实现查询用户列表 -->
<select id="findUserInIds" resultMap="userMap" parameterType="queryvo">
<include refid="defaultUser"></include>
<where>
<if test="ids != null and ids.size()>0">
<foreach collection="ids" open="and id in (" close=")" item="uid" separator=",">
#{uid}
</foreach>
</if>
</where>
</select>
mybatis一对一查询
<!-- 定义封装account和user的resultMap -->
<resultMap id="accountUserMap" type="account">
<id property="id" column="aid"></id>
<result property="uid" column="uid"></result>
<result property="money" column="money"></result>
<!-- 一对一的关系映射：配置封装user的内容-->
<association property="user" column="uid" javaType="user">
<id property="id" column="id"></id>
<result column="username" property="username"></result>
<result column="address" property="address"></result>
<result column="sex" property="sex"></result>
<result column="birthday" property="birthday"></result>
</association>
</resultMap>
mybatis一对多查询
<!-- 定义User的resultMap-->
<resultMap id="userAccountMap" type="user">
<id property="id" column="id"></id>
<result property="username" column="username"></result>
<result property="address" column="address"></result>
<result property="sex" column="sex"></result>
<result property="birthday" column="birthday"></result>
<!-- 配置user对象中accounts集合的映射 -->
<collection property="accounts" ofType="account">
<id column="aid" property="id"></id>
<result column="uid" property="uid"></result>
<result column="money" property="money"></result>
</collection>
</resultMap>
