以下 SQL 查询需要 Linq 翻译答案

【问题标题】：Need Linq translation for the following SQL Query以下 SQL 查询需要 Linq 翻译
【发布时间】：2009-10-22 13:08:05
【问题描述】：

select  colId,
        colTaskType,
        MaxID
from    tblTaskType
join    (
         select tblCheckList.colTaskTypeID,
                max(colItemNumber) MaxID
         from   tblCheckList
         group by colTaskTypeID
        ) x on coltaskTypeID = tblTaskType.colID

【问题讨论】：

标签： sql linq group-by subquery max

【解决方案1】：

假设您使用的是 linq-to-sql 并且在数据上下文中有两个表。

或多或少准确的翻译是：

var maxChecks = from checks in DataContext.tblChecklist
                group checks by checks.colTaskTypeID into g
                select new { colTaskTypeID, max = g.Group.Max(x => x.colItemNumber) };

var result = from t in DataContext.tblTaskType
             join c in maxChecks on t.colTaskTypeID equals c.colTaskTypeID
             select new { t.colId, t.colTaskTypeID, c.max };

但你可以试试：

var result = from t in DataContext.tblTaskType
             select new {
                     t.colId,
                     t.colTaskTypeID,
                     Max = (from c in DataContext.tblChecklist
                            where c.colTaskTypeID == t.colTaskTypeID
                            select c.colItemNumber).Max() };

【讨论】：