Application of several conditional constructors in MybatisPlus

version introduction

jdk 17

SpringBoot 3.1.0

druid-spring-boot-starter 1.2.4

mysql-connector 8.0.33

mybatis-plus 3.5.3.1

QueryWrapper

QueryWrapper of MybatisPlus is a tool class for constructing SQL query conditions, which provides a series of methods to facilitate condition construction. The following are commonly used methods of QueryWrapper:

1. eq(column, value): equal to query, the value of the specified field column is equal to value.
   Example: queryWrapper.eq("name", "Zhang San");

2. ne(column, value): Not equal to the query, the value of the specified field column is not equal to value.
   Example: queryWrapper.ne("age", 20);

3. gt(column, value): Greater than query, the value of the specified field column is greater than value.
   Example: queryWrapper.gt("salary", 5000);

4. ge(column, value): greater than or equal query, the value of the specified field column is greater than or equal to value.
   Example: queryWrapper.ge("create_time", "2021-01-01");

5. lt(column, value): less than query, the value of the specified field column is less than value.
   Example: queryWrapper.lt(“age”, 30);

6. le(column, value): less than or equal query, the value of the specified field column is less than or equal to value.
   Example: queryWrapper.le("salary", 10000);

7. like(column, value): Fuzzy query, the value of the specified field column contains value.
   Example: queryWrapper.like("name", "Zhang");

8. notLike(column, value): does not contain the query, the value of the specified field column does not contain value.
   Example: queryWrapper.notLike("name", "Lee");

9. in(column, values): contains the query, and the value of the specified field column is in the values ​​array.
   Example: queryWrapper.in("age", Arrays.asList(20, 30, 40));

10. notIn(column, values): does not contain the query, and the value of the specified field column is not in the values ​​array.
    Example: queryWrapper.notIn("age", Arrays.asList(50, 60, 70));

11. between(column, value1, value2): range query, the value of the specified field column is between value1 and value2.
    Example: queryWrapper.between("salary", 5000, 10000);

12. orderByAsc(column): Sort in ascending order, sort in ascending order according to the specified field column.
    Example: queryWrapper.orderByAsc("age");

13. orderByDesc(column): Sort in descending order, sort in descending order according to the specified field column.
    Example: queryWrapper.orderByDesc("salary");

14. select(columns): Specifies the field to be queried, and the parameter columns is a list of fields.
    Example: queryWrapper.select("id", "name", "age");

15. last(sql): Add a custom SQL query condition, the parameter sql is the SQL condition to be added.
    Example: queryWrapper.last("LIMIT 10");

example

QueryWrapper<User> queryWrapper = new QueryWrapper();
queryWrapper.eq("user_name", user.getUserName());

return selectList(queryWrapper);

LambdaQueryWrapper

// 创建LambdaQueryWrapper对象
LambdaQueryWrapper<User> lambdaQueryWrapper = Wrappers.lambdaQuery();

// 设置查询条件
lambdaQueryWrapper
        .eq(User::getUserName, user.getUserName()) ;

// 执行查询
List<User> userList = userMapper.selectList(lambdaQueryWrapper);
return userList;

UpdateWrapper

// 创建UpdateWrapper对象
UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();

// 设置更新条件
updateWrapper
        .eq("user_name", user.getUserName());

// 执行更新操作
User updateUser = new User();
updateUser.setPassword(user.getPassword());
int rows = update(user, updateWrapper);
return rows;

LambdaUpdateWrapper

// 创建UpdateWrapper对象
LambdaUpdateWrapper<User> updateWrapper = Wrappers.lambdaUpdate();

// 设置更新条件
updateWrapper
        .eq(User::getUserName, user.getUserName());

// 执行更新操作
User updateUser = new User();
updateUser.setPassword(user.getPassword());
int rows = update(user, updateWrapper);
return rows;

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