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我有这个 sql 查询，它完全符合我的要求，但我在 linq 中需要它。它返回一些 AVC 行并计算有多少 PersonAVCPermission 具有与其关联的状态 1

SELECT a.Id, a.Name, a.Address, COUNT(p.AVCID) AS Count
FROM AVC AS a
LEFT OUTER JOIN 
(
    SELECT PersonAVCPermission.AVCId
    FROM PersonAVCPermission
    WHERE PersonAVCPermission.Status = 1
) AS p 
ON a.Id = p.AVCId
GROUP BY a.Id, a.Name, a.Address

我在 linq 中有这个查询，它做同样的事情，除非没有 PersonAVCPermission 它仍然计为 1

var yellows = odc.PersonAVCPermissions.Where(o => o.Status == (int)AVCStatus.Yellow);

var q = from a in odc.AVCs
        from p in yellows.Where(o => o.AVCId == a.Id).DefaultIfEmpty()
        group a by new { a.Id, a.Name, a.Address } into agroup
        select new AVCListItem
        {
            Id = agroup.Key.Id,
            Name = agroup.Key.Name,
            Address = agroup.Key.Address,
            Count = agroup.Count(o => o.Id != null)
        };

我猜测使用 DefaultIfEmpty() 它将空行放在列表中然后被计算在内，所以我尝试用 (o => o.Id != null) 排除它们，但它仍然将所有内容都视为至少一个

如果我不使用 DefaultIfEmpty() 它会完全跳过计数为 0 的行

我怎样才能排除它们，还是我做错了？

4

2 回答 2

1

How about using .Any() and a Let?

var yellows = odc.PersonAVCPermissions.Where(o => o.Status == (int)AVCStatus.Yellow);

var q = from a in odc.AVCs
let Y = (from p in yellows.Where(o => o.AVCId == a.Id) select p).Any()
where Y == true
group a by new { a.Id, a.Name, a.Address } into agroup
select new AVCListItem
{
    Id = agroup.Key.Id,
    Name = agroup.Key.Name,
    Address = agroup.Key.Address,
    Count = agroup.Count(o => o.Id != null)
};
于 2013-10-25T11:04:45.087 回答
0

您不需要加入，也不需要分组：

var q = from a in odc.AVCs
        select new AVCListItem
        {
            Id = a.Id,
            Name = a.Name,
            Address = a.Address,
            Count = yellows.Where(o => o.AVCId == a.Id).Count()
        };
于 2013-10-25T11:38:42.250 回答