一、引言
那么那么那么今天来说下MP中强大的条件查询功能。
本章是基于上个案例来讲的：MyBaits-Plus 快速入门案例
二、具体操作
首先来说说基本的查询吧，根据主键或者简单的查询条件进行查询。
/**
* 通过单个ID主键进行查询
*/
@Test
public void selectById() {
User user = userMapper.selectById(1094592041087729666L);
System.out.println(user);
}
/**
* 通过多个ID主键查询
*/
@Test
public void selectByList() {
List<Long> longs = Arrays.asList(1094592041087729666L, 1094590409767661570L);
List<User> users = userMapper.selectBatchIds(longs);
users.forEach(System.out::println);
}
/**
* 通过Map参数进行查询
*/
@Test
public void selectByMap() {
Map<String, Object> params = new HashMap<>();
params.put("name", "张雨琪");
List<User> users = userMapper.selectByMap(params);
users.forEach(System.out::println);
}
MyBatis-Plus还提供了Wrapper条件构造器，具体使用看如下代码：
/**
* 名字包含雨并且年龄小于40
* <p>
* WHERE name LIKE '%雨%' AND age < 40
*/
@Test
public void selectByWrapperOne() {
QueryWrapper<User> wrapper = new QueryWrapper();
wrapper.like("name", "雨").lt("age", 40);
List<User> users = userMapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 名字包含雨
* 年龄大于20小于40
* 邮箱不能为空
* <p>
* WHERE name LIKE '%雨%' AND age BETWEEN 20 AND 40 AND email IS NOT NULL
*/
@Test
public void selectByWrapperTwo() {
QueryWrapper<User> wrapper = Wrappers.query();
wrapper.like("name", "雨").between("age", 20, 40).isNotNull("email");
List<User> users = userMapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 名字为王性
* 或者年龄大于等于25
* 按照年龄降序排序，年龄相同按照id升序排序
* <p>
* WHERE name LIKE '王%' OR age >= 25 ORDER BY age DESC , id ASC
*/
@Test
public void selectByWrapperThree() {
QueryWrapper<User> wrapper = Wrappers.query();
wrapper.likeRight("name", "王").or()
.ge("age", 25).orderByDesc("age").orderByAsc("id");
List<User> users = userMapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 查询创建时间为2019年2月14
* 并且上级领导姓王
* <p>
* WHERE date_format(create_time,'%Y-%m-%d') = '2019-02-14' AND manager_id IN (select id from user where name like '王%')
*/
@Test
public void selectByWrapperFour() {
QueryWrapper<User> wrapper = Wrappers.query();
wrapper.apply("date_format(create_time,'%Y-%m-%d') = {0}", "2019-02-14")
.inSql("manager_id", "select id from user where name like '王%'");
List<User> users = userMapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 查询王姓
* 并且年龄小于40或者邮箱不为空
* <p>
* WHERE name LIKE '王%' AND ( age < 40 OR email IS NOT NULL )
*/
@Test
public void selectByWrapperFive() {
QueryWrapper<User> wrapper = Wrappers.query();
wrapper.likeRight("name", "王").and(qw -> qw.lt("age", 40).or().isNotNull("email"));
List<User> users = userMapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 查询王姓
* 并且年龄大于20 、年龄小于40、邮箱不能为空
* <p>
* WHERE name LIKE ? OR ( age BETWEEN ? AND ? AND email IS NOT NULL )
*/
@Test
public void selectByWrapperSix() {
QueryWrapper<User> wrapper = Wrappers.query();
wrapper.likeRight("name", "王").or(
qw -> qw.between("age", 20, 40).isNotNull("email")
);
List<User> users = userMapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* (年龄小于40或者邮箱不为空) 并且名字姓王
* WHERE ( age < 40 OR email IS NOT NULL ) AND name LIKE '王%'
*/
@Test
public void selectByWrapperSeven() {
QueryWrapper<User> wrapper = Wrappers.query();
wrapper.nested(qw -> qw.lt("age", 40).or().isNotNull("email"))
.likeRight("name", "王");
List<User> users = userMapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 查询年龄为30、31、32
* WHERE age IN (?,?,?)
*/
@Test
public void selectByWrapperEight() {
QueryWrapper<User> wrapper = Wrappers.query();
wrapper.in("age", Arrays.asList(30, 31, 32));
List<User> users = userMapper.selectList(wrapper);
users.forEach(System.out::println);
}
/**
* 查询一条数据
* limit 1
*/
@Test
public void selectByWrapperNine() {
QueryWrapper<User> wrapper = Wrappers.query();
wrapper.in("age", Arrays.asList(30, 31, 32)).last("limit 1");
List<User> users = userMapper.selectList(wrapper);
users.forEach(System.out::println);
}
