mybatis insert/delete/update

记录mybatis学习

普通动态插入方式(数据库不含键,可任选字段插入):

	<insert  id="ins" parameterType="mybatistest1.Books">
		insert into books 
		<trim prefix="(" suffix=")" suffixOverrides=",">
			<if test="bno!=null">
				bno,
			</if>
			<if test="bname!=null and bname!=''">
				bname,
			</if>
			<if test="bauthor!=null and bauthor!=''">
				bauthor,
			</if>
			<if test="byear!=null">
				byear
			</if>
			 </trim> 
		 <trim prefix="values (" suffix=")" suffixOverrides=",">
			<if test="bno!=null">
				#{bno},
			</if>
			<if test="bname!=null and bname!=''">
				#{bname},
			</if>
			<if test="bauthor!=null and bauthor!=''">
				#{bauthor},
			</if>
			<if test="byear!=null">
				#{byear}
			</if>
		</trim>  
		</insert>

动态插入数据库配置文件mapper.xml,需要注意…中的小括号

<mapper namespace="book" >
	<insert  id="ins" parameterType="mybatistest1.Books">
		insert into books 
		values
		<foreach collection="list"  item="m"  separator=",">
			(#{m.bno},#{m.bname},#{m.bauthor},#{m.byear})//此时集合中为一个对象,本次运行对象名为m 需要将对象中的属性对应到表中字段名上去
			//**请高手讲解m.xx能映射到对对应字段上的原因**不胜感激
		</foreach> 
	
	</insert>

</mapper>

相关测试没问题

	@Test
	public void testt() {
		
		List<Books> list=new ArrayList<Books>();
		list.add(new Books(1,"a","a",null));
		list.add(new Books(2,"b","a",null));
		list.add(new Books(3,"c","a",null));
		
		session.insert("book.ins", list);
	}

插入数据量不宜过大,查到如果超过一兆会报错需要 通过调整MySQL安装目录下的my.ini文件中[mysqld]段的＂max_allowed_packet = 1M＂来调整

可以配合一起使用

逐条删除

	<delete id="del">
		delete from books where bno = #{bno}//普通逐条删除
		
	</delete>

批量删除

<!-- forEach : 用来循环 collection : 用来指定循环的数据的类型 可以填的值有：array,list,map item 
: 循环中为每个循环的数据指定一个别名 index : 循环中循环的下标 open : 开始 close : 结束 separator : 数组中元素之间的分隔符 -->	
 	<delete id="dell">
		delete from books 
		<where>
			bno in
			<foreach collection="list" open="(" close=")" separator="," item="m" >
				 #{m}       <!-- #{}中内容与item名字一致, -->
				 
			</foreach>
		</where>
	</delete> 

测试

	@Test
	public void testt() {
		
		List<Books> list=new ArrayList<Books>();
		list.add(new Books(1,"a","a",null));
		list.add(new Books(2,"b","a",null));
		list.add(new Books(3,"c","a",null));
		int [] aa={1,2,3};
		List<Integer> ls=new ArrayList<Integer>();
		ls.add(1);
		ls.add(2);
		
//		session.delete("book.dell", ls);
		//session.delete("book.del", aa);
		session.insert("book.ins", list);
		
	}

更新学习

首先是无条件全部更新,没意义纯属练习语法(并且set中的if应该用","分割而不是and,但语法确实能够跑通)

<update id="upd">
		update books 
		<set>//更改属性设置
			<trim suffixOverrides="and">//在更改条件间自动加入and 连接
			<if test="bno!=null">//判断是否需要更新该字段
				 bno=#{bno}
			</if>
			<if test="bname!=null and bname!=''">
				and bname=#{bname}
			</if>
			<if test="bauthor!=null and bauthor!=''">
				and bauthor=#{bauthor}
			</if>
			<if test="byear!=null and byear!=''">
				and byear=#{byear}
			</if>
			</trim>
		</set>
		//该语句能跑通,但没什么意义仅仅是语法上没什么问题而已,语句应该根据实际需要编写
		<where>
		 <trim suffixOverrides="and">
			<if test="bno!=null">
				 bno=#{bno}
			</if>
			<if test="bname!=null and bname!=''">
				and bname=#{bname}
			</if>
			<if test="bauthor!=null and bauthor!=''">
				and bauthor=#{bauthor}
			</if>
			<if test="byear!=null and byear!=''">
				and byear=#{byear}
			</if>
			</trim>
		</where>

下面是有意义更新并且 Set语句中if采用","分隔

<update id="upd">
		update books 
		<set>
			 <trim suffixOverrides=","> 
			<!-- <if test="bno!=null">
				 bno=#{bno}
			</if> -->
			<if test="bname!=null and bname!=''">
				<!-- and --> bname=#{bname},
			</if>
			<if test="bauthor!=null and bauthor!=''">
				 bauthor=#{bauthor},
			</if>
			<if test="byear!=null and byear!=''">
				 byear=#{byear},
			</if>
			 </trim> 
		</set> where bno=#{bno}

到这里增删改都做过一遍了,

首先要注意"一定要熟悉数据库语句一定要熟悉数据库语句*一定要熟悉数据库语句"

其次是对于mybatis中的标记多多联系,组合方式有很多种,前提是你能在数据库中写出正确的语句,然后利用标记拼mapper中的sql就可以了