c# - 我可以在 Entity Framework 核心和 linq 中编写查询时的案例吗？

Question

我的查询如下，(postgresql)

  SELECT split_part(grp.agerange, '*',2) as age_range,
         round(sum(salary)) AS total
  FROM
   (
       SELECT salary,
              CASE
                  WHEN(date_part('year', age(birth_date)) >  0  AND date_part('year', age(birth_date)) <= 8)   THEN  '0 - 8 age'
                  WHEN(date_part('year', age(birth_date)) >  8  AND date_part('year', age(birth_date)) <= 16)   THEN '8 - 16 age'
                  WHEN(date_part('year', age(birth_date)) >  16  AND date_part('year', age(birth_date)) <= 24)   THEN '16 - 24 age'
                  WHEN(date_part('year', age(birth_date)) >  24)  THEN '24 < age'   ELSE 'Unknown'
               END as agerange
       FROM sde.employee
    ) grp
  GROUP BY grp.agerange
  ORDER BY grp.agerange;

那么我可以使用 linq 在 Entity Framework 核心 3.0 Employee 模型中创建查询吗？

public class Employee{
   public string Id {get;set;}
   public string Name {get;set;}
   public decimal Salary {get;set;}
   public DateTime? BirthDate {get;set;}
}

从我的数据库上下文中:

var grouped = _context.Employees.Group(????

Birthdate 是 Nullable 类型。

Answer 1

您可以只使用条件运算符 ? 或 Select 语句中的 if 语句，然后按该结果分组....

var grouped = _context.Employees
    .Select(e => new { AgeRange = e.birth_date.Year > 24 ? "24 < age" : etc.});
    .Group(e => e.AgeRange);