where标签:
1、自动加上where
2、如果where子句以and或者or开头,则自动删除第一个and或or
trim标签:
功能和 where 元素类似,提供了前缀,后缀功能,更加灵活;
StudentMapper.xml
<select id="searchStudents3" parameterType="Map" resultMap="StudentResult">
select * from t_student
<where>
<if test="gradeId!=null">
gradeId=#{gradeId}
</if>
<if test="name!=null">
and name like #{name}
</if>
<if test="age!=nulll">
and age=#{age}
</if>
</where>
</select>
<select id="searchStudents4" parameterType="Map" resultMap="StudentResult">
select * from t_student
<trim prefix="where" prefixOverrides="and|or">
<if test="gradeId!=null">
gradeId=#{gradeId}
</if>
<if test="name!=null">
and name like #{name}
</if>
<if test="age!=nulll">
and age=#{age}
</if>
</trim>
</select>
junit测试
@Test
public void testSearchStudents3() {
logger.info("添加学生(带条件)");
Map<String,Object> map=new HashMap<String,Object>();
map.put("gradeId", 2);
map.put("name", "%李%");
map.put("age", 11);
List<Student> studentList=studentMapper.searchStudents3(map);
for(Student student:studentList){
System.out.println(student);
}
}
@Test
public void testSearchStudents4() {
logger.info("添加学生(带条件)");
Map<String,Object> map=new HashMap<String,Object>();
map.put("gradeId", 2);
// map.put("name", "%李%");
// map.put("age", 11);
List<Student> studentList=studentMapper.searchStudents4(map);
for(Student student:studentList){
System.out.println(student);
}
}