sql-server - 将SQL CASE WHEN语句加组语句转换为LINQ

Question

如何使用流利的 linq 语法编写“case when”sql 语句？

select QueueItem, COUNT(*) as [Count],
SUM(CASE WHEN Queued = 0 THEN 1 ELSE 0 END) AS [Sent],
SUM(CASE WHEN Queued = 1 THEN 1 ELSE 0 END) AS Queued,
SUM(CASE WHEN Success = 1 THEN 1 ELSE 0 END) AS Exported,
SUM(CASE WHEN Success = 0 THEN 1 ELSE 0 END) AS Failed
from ExportQueue x
group by QueueItem

是否有一些程序可以将 SQL 转换为 LINQ？也许是 LinqPad？

Answer 1

好的，像这样。不过，我需要一些信息来确定

有点排队吗？这在 linq 中有所不同，而在 SQL 中却没有。 我也不知道您的上下文名称，但您应该明白了。

var query = Context.ExportQueues.Select(x => new { 
  QueueItem = x.QueueItem, 
  Sent = !x.Queued ? 1 : 0,
  Queued = x.Queued ? 1 : 0,
  Exported = x.Success ? 1 : 0,
  Failed = !x.Success ? 1 : 0 })
.GroupBy(x => x.QueueItem)
.Select(g => new { 
  QueueItem = g.Key,
  Sent = g.Sum(x => x.Sent),
  Queued = g.Sum(x => x.Queued),
  Exported = g.Sum(x => x.Exported),
  Failed = g.Sum(x => x.Failed)
}).ToList();

EDIT 您还可以通过在查询中即时进行案例来组合这些。我总是倾向于先按上面的方式写出来，因为如果有错误，更复杂的聚合可能有点难以调试:

var query = Context.ExportQueues
.GroupBy(x => x.QueueItem)
.Select(g => new { 
  QueueItem = g.Key,
  Sent = g.Sum(x => !x.Queued ? 1 : 0),
  Queued = g.Sum(x => x.Queued ? 1 : 0),
  Exported = g.Sum(x => x.Success ? 1 : 0),
  Failed = g.Sum(x => !x.Success ? 1 : 0 )
}).ToList();