Question

如何将此SQL查询转换为LINQ？

到目前为止，我已经提出了这一行：

SELECT eg.Name Name, sum(bi.PlannedAmount) Amount
FROM BudgetItem bi, Expense e, ExpenseGroup eg
WHERE Discriminator = 'ExpenseItem' AND
bi.ExpenseId = e.Id AND
e.ExpenseGroupId = eg.id AND
bi.MonthlyBudgetId = 1
GROUP BY eg.Name

但我仍然无法弄清楚用什么表达来添加＆＃39; bi.MonthlyBudgetItem = 1＆＃39;。

有人有想法吗？

编辑＃1： 我忘了提到实体之间的关系。每个 ExpenseGroup 都有许多费用，每个费用都有许多 BudgetItems 。

所以，ExpenseGroup =＆gt;费用=＆gt; BudgetItems

编辑＃2： 我使用Entity Framework，每个ExpenseGroup都有一个Expense对象集合（每个Expense都有一个ExpenseGroup对象），每个Expense都有一个BudgetItem对象集合（每个BudgetItem对象都有一个Expense对象）。

Answer 1

我想这样的事情应该这样做：

var result = context
        .ExpenseGroups
        .Where(x => x.Discriminator == 'ExpenseItem' && 
            x.bi.ExpenseId == e.Id && 
            x.e.ExpenseGroupId == eg.id &&
            x.bi.MonthlyBudgetId == 1)
        .GroupBy(eg => eg.Id, (s) => new { Name = s.Name, Amount = s.Expenses.SelectMany(e => e.Items).Sum(i => i.PlannedAmount) })
        .ToList();

Answer 2

类似于此......

var result = (from g in context.ExpenseGroups
              where g.Expense.BudgetItem.MonthlyBudgetId == 1
              select g)
        .GroupBy(eg => eg.Id, (s) => new { Name = s.Name, Amount = s.Expenses.SelectMany(e => e.Items).Sum(i => i.PlannedAmount) })
        .ToList();

或

var result = context.ExpenseGroups
             .Where(g => g.Expense.BudgetItem.MonthlyBudgetId == 1)
             .GroupBy(eg => eg.Id, (s) => new { Name = s.Name, Amount = s.Expenses.SelectMany(e => e.Items).Sum(i => i.PlannedAmount) })
        .ToList();

Answer 3

您实际上在SQL查询中执行inner join，因此在您的linq查询中也是如此。这应该有效： -

var result = from bi in context.BudgetItem
             join e in context.Expense 
             on bi.ExpenseId equals e.Id 
             where bi.MonthlyBudgetId == 1
             join eg in ExpenseGroup 
             on e.ExpenseGroupId equals eg.id 
             group new { bi, eg } by eg.Name into g
             select new 
                   {
                         Name = g.Key,
                         Amount = g.Sum(x => x.bi.PlannedAmount)
                   };

如何将此SQL查询转换为LINQ？

3 个答案: