这是我参与「掘金日新计划 · 6 月更文挑战」的第19天 ,点击查看活动详情
一、wapper介绍
Wrapper ： 条件构造抽象类，最顶端父类
AbstractWrapper ： 用于查询条件封装，生成 sql 的 where 条件
QueryWrapper ： 查询条件封装
UpdateWrapper ： Update 条件封装
AbstractLambdaWrapper ： 使用Lambda 语法
LambdaQueryWrapper ：用于Lambda语法使用的查询Wrapper
LambdaUpdateWrapper ： Lambda 更新封装Wrapper
\
@RunWith(SpringRunner.class)
@SpringBootTest
public class QueryWrapperTests {
@Autowired
private UserMapper userMapper;
}
二、AbstractWrapper
**
**注意： 以下条件构造器的方法入参中的 column 均表示数据库字段
1、ge、gt、le、lt、isNull、isNotNull
@Test
public void testDelete() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper
.isNull("name")
.ge("age", 12)
.isNotNull("email");
int result = userMapper.delete(queryWrapper);
System.out.println("delete return count = " + result);
}
SQL：UPDATE user SET deleted=1 WHERE deleted=0 AND name IS NULL AND age >= ? AND email IS NOT NULL
**
**
2、eq、ne
注意： seletOne返回的是一条实体记录，当出现多条时会报错
@Test
public void testSelectOne() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.eq("name", "Tom");
User user = userMapper.selectOne(queryWrapper);
System.out.println(user);
}
SELECT id,name,age,email,create_time,update_time,deleted,version FROM user WHERE deleted=0 AND name = ?
**
**
3、between、notBetween
包含大小边界
@Test
public void testSelectCount() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.between("age", 20, 30);
Integer count = userMapper.selectCount(queryWrapper);
System.out.println(count);
}
SELECT COUNT(1) FROM user WHERE deleted=0 AND age BETWEEN ? AND ?
**
**
4、allEq
@Test
public void testSelectList() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
Map<String, Object> map = new HashMap<>();
map.put("id", 2);
map.put("name", "Jack");
map.put("age", 20);
queryWrapper.allEq(map);
List<User> users = userMapper.selectList(queryWrapper);
users.forEach(System.out::println);
}
SELECT id,name,age,email,create_time,update_time,deleted,version
FROM user WHERE deleted=0 AND name = ? AND id = ? AND age = ?
**
**
5、like、notLike、likeLeft、likeRight
selectMaps返回Map集合列表
@Test
public void testSelectMaps() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper
.notLike("name", "e")
.likeRight("email", "t");
List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);//返回值是Map列表
maps.forEach(System.out::println);
}
SELECT id,name,age,email,create_time,update_time,deleted,version
FROM user WHERE deleted=0 AND name NOT LIKE ? AND email LIKE ? \
**
**
6、in、notIn、inSql、notinSql、exists、notExists
in、notIn：
notIn("age",{1,2,3})--->age not in (1,2,3) notIn("age", 1, 2, 3)--->age not in (1,2,3)
inSql、notinSql：可以实现子查询
- 例:
inSql("age", "1,2,3,4,5,6")--->age in (1,2,3,4,5,6) - 例:
inSql("id", "select id from table where id < 3")--->id in (select id from table where id < 3)
@Test
public void testSelectObjs() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//queryWrapper.in("id", 1, 2, 3);
queryWrapper.inSql("id", "select id from user where id < 3");
List<Object> objects = userMapper.selectObjs(queryWrapper);//返回值是Object列表
objects.forEach(System.out::println);
}
SELECT id,name,age,email,create_time,update_time,deleted,version
FROM user WHERE deleted=0 AND id IN (select id from user where id < 3)
\
7、or、and
注意： 这里使用的是 UpdateWrapper
不调用or则默认为使用 and 连\
@Test
public void testUpdate1() {
//修改值
User user = new User();
user.setAge(99);
user.setName("Andy");
//修改条件
UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
userUpdateWrapper
.like("name", "h")
.or()
.between("age", 20, 30);
int result = userMapper.update(user, userUpdateWrapper);
System.out.println(result);
}
UPDATE user SET name=?, age=?, update_time=? WHERE deleted=0 AND name LIKE ? OR age BETWEEN ? AND ?
\
8、嵌套or、嵌套and
这里使用了lambda表达式，or中的表达式最后翻译成sql时会被加上圆括号
@Test
public void testUpdate2() {
//修改值
User user = new User();
user.setAge(99);
user.setName("Andy");
//修改条件
UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
userUpdateWrapper
.like("name", "h")
.or(i -> i.eq("name", "李白").ne("age", 20));
int result = userMapper.update(user, userUpdateWrapper);
System.out.println(result);
}
UPDATE user SET name=?, age=?, update_time=?
WHERE deleted=0 AND name LIKE ?
OR ( name = ? AND age <> ? )
\
9、orderBy、orderByDesc、orderByAsc
@Test
public void testSelectListOrderBy() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.orderByDesc("id");
List<User> users = userMapper.selectList(queryWrapper);
users.forEach(System.out::println);
}
SELECT id,name,age,email,create_time,update_time,deleted,version
FROM user WHERE deleted=0 ORDER BY id DESC
\
10、last
直接拼接到 sql 的最后\
注意： 只能调用一次,多次调用以最后一次为准 有sql注入的风险,请谨慎使用
@Test
public void testSelectListLast() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.last("limit 1");
List<User> users = userMapper.selectList(queryWrapper);
users.forEach(System.out::println);
}
SELECT id,name,age,email,create_time,update_time,deleted,version
FROM user WHERE deleted=0 limit 1
\
11、 指定要查询的列
@Test
public void testSelectListColumn() {
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.select("id", "name", "age");
//可以使用vo对象代替User对象，使返回结果更准确，占用更少的数据流量
//List<User> users = userMapper.selectList(queryWrapper);
//users.forEach(System.out::println);
//也可以返回map集合对象
List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);//返回值是Map列表
maps.forEach(System.out::println);
}
SELECT id,name,age FROM user WHERE deleted=0
\
12、set、setSql
最终的sql会合并 user.setAge()，以及 userUpdateWrapper.set() 和 setSql() 中 的字段
@Test
public void testUpdateSet() {
//修改值
User user = new User();
user.setAge(99);
//修改条件
UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
userUpdateWrapper
.like("name", "h")
.set("name", "老李头")//除了可以查询还可以使用set设置修改的字段
.setSql(" email = '123@qq.com'");//可以有子查询
int result = userMapper.update(user, userUpdateWrapper);
}
UPDATE user SET age=?, update_time=?, name=?, email = '123@qq.com' WHERE deleted=0 AND name LIKE ?
