文章目录
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 ： Entity 对象封装操作类，不是用lambda语法
UpdateWrapper ： Update 条件封装，用于Entity对象更新操作
AbstractLambdaWrapper ： Lambda 语法使用 Wrapper统一处理解析 lambda 获取 column。
LambdaQueryWrapper ：看名称也能明白就是用于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 deleteTest(){
//创建条件构造器对象
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
//以下条件构造器的方法入参中的 column 均表示数据库字段
//ge、gt、le、lt、isNull、isNotNull
/**
* ge(greater than or equal):大于等于
* gt(greater than)；大于
* le(less than or equal):小于等于
* lt(less than):小于
*/
//条件为email为空，name不为空，age大于等于12小于等于22
// WHERE
// deleted=0
// AND name IS NOT NULL
// AND age >= 12
// AND age <= 22
queryWrapper
.isNull("email")
.isNotNull("name")
.ge("age",12)
.le("age",22);
int row = userMapper.delete(queryWrapper);
System.out.println(row);
}
Execute SQL：UPDATE user SET deleted=1 WHERE deleted=0 AND email IS NULL AND name IS NOT NULL AND age >= 12 AND age <= 22
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 selectOneTest(){
//eq、ne即equal 、not equal
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper
.eq("id",1);
//selectOne正常返回一条记录，返回多条记录时会报错
User user = userMapper.selectOne(queryWrapper);
System.out.println(user);
}
Execute SQL：SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND id = 1
3、between、notBetween
包含大小边界
@Test
public void selectCountTest(){
//between、notBetween
//包含大小边界
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper
.between("age",18,22);
// WHERE
// deleted=0
// AND age BETWEEN 18 AND 22
List<User> users = userMapper.selectList(queryWrapper);
users.forEach(System.out :: println);
}
Execute SQL：SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND age BETWEEN 18 AND 22
4、allEq
@Test
public void testSelectList(){
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
HashMap<String, Object> Map = new HashMap<>();
//条件封装进Map
Map.put("id",4);
Map.put("name","Sandy");
Map.put("age",21);
//allEq:全匹配
queryWrapper.allEq(Map);
List<User> users = userMapper.selectList(queryWrapper);
users.forEach(System.out ::println);
}
Execute SQL：SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND name = ‘Sandy’ AND id = 4 AND age = 21
5、like、notLike、likeLeft、likeRight
selectMaps返回Map集合列表
@Test
public void testSelectMaps(){
//like、notLike、likeLeft、likeRight
//selectMaps返回Map集合列表
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper
.notLike("name","e") //LIKE '%e%'
.likeRight("email","t");//LIKE 't%',同理likeLeft为LIKE '%t'
//Execute SQL：SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND name NOT LIKE '%e%' AND email LIKE 't%'
List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);
maps.forEach(System.out ::println);
}
Execute SQL：SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND name NOT LIKE ‘%e%’ AND email LIKE ‘t%’
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()//不调用or则默认为使用 and 连
.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");
List<User> users = userMapper.selectList(queryWrapper);
users.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 ?