MyBatis的增删改查操作

Posted 2022-02-20 ly570

搭建好mybatis之后 进行对数据库的操作

添加语句
在映射文件中添加语句

<mapper namespace="com.wn.dao.StudentDao">
<insert id="insertStudent" parameterType="StudentBean">
insert into student(name,age,score) values(#name,#age,#score)
</insert>
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映射文件要放在与接口一个目录下
namespace：必须是对应接口的全限定名
id ：dao中的方法名字
parameterType：传入的参数类型 可以省略

添加语句后 获取主键的值 赋值给主键

<insert id="insertStudentGetId" parameterType="StudentBean">
insert into student(name,age,score) values(#name,#age,#score)
<!-- keyProperty:查询结果赋值给studentbean的id属性
resultType：返回结果的数据类型
order：执行顺序 mysql在数据添加后
-->
<selectKey keyProperty="id" resultType="int" order="AFTER">
select @@identity
</selectKey>
</insert>
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2.删除语句

<update id="updateStudent" >
update student set name=#name ,age=#age,score=#score
where id = #id
</update>
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3.查询语句

/**
* 静态参数
* @param student
*/
void insertStudent(StudentBean student);
List<StudentBean> selectStudentAll();
//根据姓名模糊查询
List<StudentBean> selectStudentByName(String name);

//多参数查询 使用map作为方法参数
List<StudentBean> selectStuByMap1(Map<String, Object> map);
List<StudentBean> selectStuByMap2(Map<String, Object> map);

List<StudentBean> selectStuByParameters1(String name , int age);
List<StudentBean> selectStuByParameters2(String name , StudentBean student);
List<StudentBean> selectStuByParameters3(@Param("name") String name , @Param("age")int age);
List<StudentBean> selectStuByParameters4(@Param("name") String name , @Param("student") StudentBean student);

 

 

<select id="selectStudentAll" resultType="StudentBean">
select * from student
</select>
<select id="selectStudentByName" resultType="StudentBean">
select * from student where name like ‘%‘ #name ‘%‘
</select>

<select id="selectStuByMap1" resultType="StudentBean">
<!-- 查询的参数是Map #map的key 使用的数据是key对应的value-->
select * from student where name like ‘%‘ #name ‘%‘ and age>#age
</select>

<select id="selectStuByMap2" resultType="StudentBean">
<!-- 查询的参数是Map #map的key 使用的数据是key对应的value
map的key是student，value是student对象-->
select * from student where name like ‘%‘ #name ‘%‘ and age > #student.age
</select>

<select id="selectStuByParameters1" resultType="StudentBean">
select * from student where name like ‘%‘ #0 ‘%‘ and age > #1
</select>

<select id="selectStuByParameters2" resultType="StudentBean">
select * from student where name like ‘%‘ #0 ‘%‘ and age > #1.age
</select>
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动态参数

/**
* 动态参数
*/
//mybatis 动态参数类似域jstl《c:》

//if拼接 sql语句要跟上 where 1 =1
List<StudentBean> selectStudentByIf(StudentBean student);

<select id="selectStudentByIf" resultType="StudentBean">
select * from student where 1=1
<if test="name!=null and name!=‘‘">
and name like ‘%‘ #name ‘%‘
</if>
<if test="age>0">
and age > #age
</if>
</select>

//不生成 1= 1 提高效率 自动在sql语句拼接的时候加上where 关键字
List<StudentBean> selectStudentByWhere(StudentBean student);

<select id="selectStudentByWhere" resultType="StudentBean">
select * from student
<where>
<if test="name!=null and name!=‘‘">
and name like ‘%‘ #name ‘%‘
</if>
<if test="age>0">
and age > #age
</if>
</where>
</select>

//多选一
List<StudentBean> selectStudentByChoose(StudentBean student);

<select id="selectStudentByChoose" resultType="StudentBean">
select * from student
<choose>
<when test="name!=null and name!=‘‘">
where name like ‘%‘ #name ‘%‘
</when>
<when test="age>0">
where age > #age
</when>
<otherwise>
where 1 = 2
</otherwise>
</choose>
</select>

List<StudentBean> selectStudentByForeachArray(int[] ids);

<select id="selectStudentByForeachArray" resultType="StudentBean">
select * from student
<if test="array!=null and array.length>0">
where id in
<foreach collection="array" item="id" open="(" close=")" separator=",">
#id
</foreach>
</if>
</select>

List<StudentBean> selectStudentByForeachList(List<Integer> ids);

<select id="selectStudentByForeachList" resultType="StudentBean">
select * from student
<if test="list!=null and list.size>0">
where id in
<foreach collection="list" item="id" open="(" close=")" separator=",">
#id
</foreach>
</if>
</select>

List<StudentBean> selectStudentByForeachStudent(List<StudentBean> students);

<select id="selectStudentByForeachStudent" resultType="StudentBean">
select * from student
<if test="list!=null and list.size>0">
where id in
<foreach collection="list" item="student" open="(" close=")" separator=",">
#student.id
</foreach>
</if>
</select>

List<StudentBean> selectStudentBySqlFragement();

<select id="selectStudentBySqlFragement" resultType="StudentBean">
select <include refid="fragement" /> student
</select>
<sql id="fragement"> * from</sql>

//统计一张表的总数据条数 分页的总条数
int selectStudentCount();

<select id="selectStudentCount" resultType="int">
select count(*) from student
</select>

<!-- 动态参数 -->
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