在数据库建立一个employee表，实现以下功能：（基于案例一）
1.实现多条件查询，根据员工的姓名和年龄筛选
（1）当用户输入姓名不为空，年龄为空时，则只根据姓名查询；
（2）当用户输入年龄不为空，姓名为空时，则只根据年龄查询；
（3）当用户输入年龄和姓名都不为空时，根据年龄姓名同时查询；
（4）当用户输入年龄和姓名都为空时，则查询出所有职位不为空的的员工信息；
2.查询id=1,2,5,6的员工信息
3.单条件查询出所有id值小于5的员工的信息；
4.查询出年龄为26且职位为员工的员工信息；
代码实现：
使用了MyBatis动态SQL中的常用元素<if>、<choose>、<when>、<otherwise>、<foreach>
1.EmployeeMapper.xml文件
<!--根据年龄和姓名查询-->
<select id="findByNameOrAge" parameterType="org.example.pojo.Employee" resultType="org.example.pojo.Employee">
select * from employee where 1 = 1
<!--1.（3）当年龄姓名都不为空时，根据年龄姓名同时查询-->
<if test="name != null and name != '' and age != null and age != ''">
<!--当写成“and name = #{name} or age = #{age}”时，只能查询到姓名符合的信息,调换位置后才能同时查询出符合信息-->
and age = #{age} or name = #{name}
</if>
<!--1.多条件查询-->
<choose>
<when test="name != null and name != ''">
and name like concat('%',#{name},'%')
</when>
<when test="age != null and age != ''">
and age = #{age}
</when>
<otherwise>
and position is not null
</otherwise>
</choose>
</select>
<!--2.查询id=1,2,5,6的员工信息-->
<select id="findByArray" parameterType="java.util.Arrays" resultType="org.example.pojo.Employee">
select * from employee where id in
<foreach collection="array" item="id" index="index" open="(" separator="," close=")">
#{id}
</foreach>
</select>
<!--3.查询id小于5的员工信息-->
<select id="findByList" parameterType="java.util.List" resultType="org.example.pojo.Employee">
select * from employee where id in
<foreach collection="list" item="id" index="index" open="(" separator="," close=")">
#{id}
</foreach>
</select>
<!--4.查询出年龄为26且职位为员工的员工信息-->
<select id="findByMap" parameterType="java.util.Map" resultType="org.example.pojo.Employee">
select * from employee where age = #{age} and position = #{position} and id in
<foreach collection="id" item="roleMap" index="index" open="(" separator="," close=")">
#{roleMap}
</foreach>
</select>2.测试类findTest
public class findTest {
SqlSession sqlSession = MyBatisUtils.getSession();
@Test
public void findByNameOrAge(){
Employee employee = new Employee();
employee.setName("张三");
employee.setAge(22);
List<Employee> list = sqlSession.selectList("findByNameOrAge",employee);
for (Employee employee1:list){
System.out.println(employee1);
}
sqlSession.close();
}
@Test
public void findByArray(){
Integer[] ids = {1,2,5,6};
List<Employee> list = sqlSession.selectList("findByArray",ids);
for (Employee employee:list){
System.out.println(employee);
}
//找不到的时候呢？
sqlSession.close();
}
@Test
public void findByList(){
List<Integer> list = new ArrayList<>();
for (int i = 0;i < 5;i++){
list.add(i);
}
List<Employee> employees = sqlSession.selectList("findByList",list);
for (Employee employee:employees){
System.out.println(employee);
}
sqlSession.close();
}
@Test
public void findByMap(){
List<Integer> list = new ArrayList<>();
list.add(1);
list.add(3);
list.add(5);
list.add(6);
Map<String ,Object> map = new HashMap<>();
map.put("id",list);
map.put("age","26");
map.put("position","员工");
List<Employee> employees = sqlSession.selectList("findByMap",map);
for (Employee employee:employees){
System.out.println(employee);
}
sqlSession.close();
}
}
