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Conditional constructor ~wapper
2022-08-02 07:54:00 【Fruits of IT Midsummer】
目录
1 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：用于Lambda更新封装Wrapper
2 条件查询
2.1 组装查询条件
@Test
public void test01(){
//查询用户名包含a,年龄在20到30之间,邮箱信息不为null的用户信息
//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age BETWEEN ? AND ? AND email IS NOT NULL)
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.like("user_name", "a")
.between("age", 20, 30)
.isNotNull("email");
List<User> list = userMapper.selectList(queryWrapper);
list.forEach(System.out::println);
}sql拼接如下：
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age BETWEEN ? AND ? AND email IS NOT NULL)
==> Parameters: %a%(String), 20(Integer), 30(Integer)
<== Total: 02.2 组装排序条件
@Test
public void test02(){
//查询用户信息,按照年龄的降序排序,若年龄相同,则按照id升序排序
//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 ORDER BY age DESC,uid ASC
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.orderByDesc("age")
.orderByAsc("uid");
List<User> list = userMapper.selectList(queryWrapper);
list.forEach(System.out::println);
}sql拼接如下：
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 ORDER BY age DESC,uid ASC
==> Parameters:
<== Columns: id, name, age, email, is_deleted
<== Row: 6, ybc6, 26, null, 0
<== Row: 5, ybc5, 25, null, 0
<== Row: 3, ybc3, 23, null, 0
<== Row: 2, ybc2, 22, null, 0
<== Row: 4, ybc4, 22, null, 0
<== Row: 1, ybc1, 21, null, 0
<== Total: 6It can be seen that they are sorted in descending order of age,当年龄相同的时候,则按照id的升序排列.
2.3 组装删除条件
@Test
public void test03(){
//删除邮箱地址为null的用户信息
//UPDATE t_user SET is_deleted=1 WHERE is_deleted=0 AND (email IS NULL)
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.isNull("email");
int result = userMapper.delete(queryWrapper);
System.out.println("result:"+result);
}sql拼接如下：
==> Preparing: UPDATE t_user SET is_deleted=1 WHERE is_deleted=0 AND (email IS NULL)
==> Parameters:
<== Updates: 6
Closing non transactional SqlSession [[email protected]]
result:6注意：This is really just a logical delete.
2.4 queryWrapper实现修改功能
@Test
public void test04(){
//将（年龄大于20并且用户名中包含有a）或邮箱为null的用户信息修改
//UPDATE t_user SET user_name=?, email=? WHERE is_deleted=0 AND (age > ? AND user_name LIKE ? OR email IS NULL)
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.gt("age", 20)
.like("user_name", "a")
.or()
.isNull("email");
User user = new User();
user.setName("小明");
user.setEmail("[email protected]");
int result = userMapper.update(user, queryWrapper);
System.out.println("result:"+result);
}sql拼接如下：
==> Preparing: UPDATE t_user SET user_name=?, email=? WHERE is_deleted=0 AND (age > ? AND user_name LIKE ? OR email IS NULL)
==> Parameters: 小明(String), [email protected](String), 20(Integer), %a%(String)
<== Updates: 0
Closing non transactional SqlSession [[email protected]]
result:0可见：update(@Param("et") T entity, @Param("ew") Wrapper<T> updateWrapper)
When executing this syntax,The previous value that needs to be modified,Followed by qualified data.
2.5 条件的优先级
有些时候,Although we spliced a lot of conditions,However, arranging the execution order of the conditions reasonably can help us optimize the query speed to a large extent.
@Test
public void test05(){
//将用户名中包含有a并且（年龄大于20或邮箱为null）的用户信息修改
//lambda中的条件优先执行
//UPDATE t_user SET user_name=?, email=? WHERE is_deleted=0 AND (user_name LIKE ? AND (age > ? OR email IS NULL))
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.like("user_name", "a")
.and(i->i.gt("age",20).or().isNull("email"));
User user = new User();
user.setName("小红");
user.setEmail("[email protected]");
int result = userMapper.update(user, queryWrapper);
System.out.println("result:"+result);
}sql拼接如下：
==> Preparing: UPDATE t_user SET user_name=?, email=? WHERE is_deleted=0 AND (user_name LIKE ? AND (age > ? OR email IS NULL))
==> Parameters: 小红(String), [email protected](String), %a%(String), 20(Integer)
<== Updates: 0
Closing non transactional SqlSession [[email protected]]
result:0注意：在mybatisplus中,lambda中的条件优先执行.Because you can see the stitchingsql语句中age和emailinside a parenthesis.
2.6 组装select语句
@Test
public void test06(){
//查询用户的用户名、年龄、邮箱信息
//SELECT user_name,age,email FROM t_user WHERE is_deleted=0
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.select("user_name", "age", "email");
List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);
maps.forEach(System.out::println);
}拼接sql如下：
==> Preparing: SELECT user_name,age,email FROM t_user WHERE is_deleted=0
==> Parameters:
<== Total: 02.7 组装子查询
@Test
public void test07(){
//查询id小于等于100的用户信息
//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (uid IN (select uid from t_user where uid <= 100))
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.inSql("uid", "select uid from t_user where uid <= 100");
List<User> list = userMapper.selectList(queryWrapper);
list.forEach(System.out::println);
}拼接sql如下：
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (uid IN (select uid from t_user where uid <= 100))
==> Parameters:
<== Total: 02.8 使用updateWrapper实现修改功能
@Test
public void test08(){
//将用户名中包含有a并且（年龄大于20或邮箱为null）的用户信息修改
UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
updateWrapper.like("user_name", "a")
.and(i -> i.gt("age", 20).or().isNull("email"));
updateWrapper.set("user_name", "小黑").set("email","[email protected]");
int result = userMapper.update(null, updateWrapper);
System.out.println("result："+result);
}拼接sql如下：
==> Preparing: UPDATE t_user SET user_name=?,email=? WHERE is_deleted=0 AND (user_name LIKE ? AND (age > ? OR email IS NULL))
==> Parameters: 小黑(String), [email protected](String), %a%(String), 20(Integer)
<== Updates: 0
Closing non transactional SqlSession [[email protected]]
result：02.9 使用condition组装条件
@Test
public void test10(){
String username = "a";
Integer ageBegin = null;
Integer ageEnd = 30;
QueryWrapper<User> queryWrapper = new QueryWrapper<>();
queryWrapper.like(StringUtils.isNotBlank(username), "user_name", username)
.ge(ageBegin != null, "age", ageBegin)
.le(ageEnd != null, "age", ageEnd);
List<User> list = userMapper.selectList(queryWrapper);
list.forEach(System.out::println);
}拼接sql如下：
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age <= ?)
==> Parameters: %a%(String), 30(Integer)
<== Total: 02.10 LambdaQueryWrapper
@Test
public void test11(){
//SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age <= ?)
String username = "a";
Integer ageBegin = null;
Integer ageEnd = 30;
LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
queryWrapper.like(StringUtils.isNotBlank(username), User::getName, username)
.ge(ageBegin != null, User::getAge, ageBegin)
.le(ageEnd != null, User::getAge, ageEnd);
List<User> list = userMapper.selectList(queryWrapper);
list.forEach(System.out::println);
}拼接sql如下：
==> Preparing: SELECT uid AS id,user_name AS name,age,email,is_deleted FROM t_user WHERE is_deleted=0 AND (user_name LIKE ? AND age <= ?)
==> Parameters: %a%(String), 30(Integer)
<== Total: 02.11 LambdaUpdateWrapper
@Test
public void test12(){
//将用户名中包含有a并且（年龄大于20或邮箱为null）的用户信息修改
LambdaUpdateWrapper<User> updateWrapper = new LambdaUpdateWrapper<>();
updateWrapper.like(User::getName, "a")
.and(i -> i.gt(User::getAge, 20).or().isNull(User::getEmail));
updateWrapper.set(User::getName, "小黑").set(User::getEmail,"[email protected]");
int result = userMapper.update(null, updateWrapper);
System.out.println("result："+result);
}拼接sql如下：
==> Preparing: UPDATE t_user SET user_name=?,email=? WHERE is_deleted=0 AND (user_name LIKE ? AND (age > ? OR email IS NULL))
==> Parameters: 小黑(String), [email protected](String), %a%(String), 20(Integer)
<== Updates: 0
Closing non transactional SqlSession [[email protected]]
result：0边栏推荐
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