MyBatis-Plus includes a robust set of Wrapper classes for creating complex database query conditions. The primary Wrapper types are:

• QueryWrapper: Builds query conditions with support for equality, inequality, greater-than, less-than, and other oeprations. It allows chaining multiple conditions and combining them with and and or logic.
• UpdateWrapper: Constructs conditions for update operations, specifying which records to modify.
• LambdaQueryWrapper: A query wrapper that uses lambda expressions to reference entity class properties, eliminating hard-coded column names and improving code readability.
• LambdaUpdateWrapper: An update wrapper that similarly employs lambda expressions for specifying fields and conditions.

Common conditional methods include:

• eq (equals)

  QueryWrapper<Employee> wrapper = new QueryWrapper<>();
  wrapper.eq("department", "Engineering");
  // Or using lambda
  LambdaQueryWrapper<Employee> lambdaWrapper = new LambdaQueryWrapper<>();
  lambdaWrapper.eq(Employee::getDepartment, "Engineering");
  

  Generated SQL: SELECT * FROM employee WHERE department = 'Engineering'

• ne (not equals)

  wrapper.ne("status", "inactive");
  lambdaWrapper.ne(Employee::getStatus, "inactive");
  

  Generated SQL: SELECT * FROM employee WHERE status <> 'inactive'

• gt (greater than)

  wrapper.gt("salary", 50000);
  lambdaWrapper.gt(Employee::getSalary, 50000);
  

  Generated SQL: SELECT * FROM employee WHERE salary > 50000

• ge (greater than or equal to)

  wrapper.ge("years_of_service", 5);
  lambdaWrapper.ge(Employee::getYearsOfService, 5);
  

  Generated SQL: SELECT * FROM employee WHERE years_of_service >= 5

• lt (less than)

  wrapper.lt("remaining_vacation", 10);
  lambdaWrapper.lt(Employee::getRemainingVacation, 10);
  

  Generated SQL: SELECT * FROM employee WHERE remaining_vacation < 10

• le (less than or equal to)

  wrapper.le("age", 65);
  lambdaWrapper.le(Employee::getAge, 65);
  

  Generated SQL: SELECT * FROM employee WHERE age <= 65

• between

  wrapper.between("hire_date", "2023-01-01", "2023-12-31");
  lambdaWrapper.between(Employee::getHireDate, "2023-01-01", "2023-12-31");
  

  Generated SQL: SELECT * FROM employee WHERE hire_date BETWEEN '2023-01-01' AND '2023-12-31'

• notBetween

  wrapper.notBetween("project_id", 100, 200);
  lambdaWrapper.notBetween(Employee::getProjectId, 100, 200);
  

  Generated SQL: SELECT * FROM employee WHERE project_id NOT BETWEEN 100 AND 200

• like

  wrapper.like("last_name", "Smith");
  lambdaWrapper.like(Employee::getLastName, "Smith");
  

  Generated SQL: SELECT * FROM employee WHERE last_name LIKE '%Smith%'