[英]How to do left outer joins with DbLinq and SQLite?
我試過了
db.Table1.GroupJoin(db.Table2,
t1 => t1.Id,
t2 => t2.t1Id,
(t1,g) => new { t1, g })
.Where(item => !item.g.Any())
.Select(item => item.t1);
但它返回了 0 個結果。 我正在嘗試編寫一些生成以下 SQL 代碼(或類似代碼)的東西
SELECT t1.*
FROM Table1 as t1
LEFT OUTER JOIN Table2 as t2
ON t1.Id = t2.t1Id
WHERE IsNull(t2.Id);
看起來您想要的結果是從Table1
中識別在與Table2
的左外連接期間沒有結果的項目。
用流利的符號表示,該方法類似於以下內容:
var query = db.Table1.GroupJoin(db.Table2,
t1 => t1.Id,
t2 => t2.t1Id,
(t1, joined) => new { t1, joined }
)
.SelectMany(r => r.joined.DefaultIfEmpty(), (r, j) => new
{
r.t1,
j
})
.Where(r => r.j == null)
.Select(r => r.t1);
在查詢語法中:
var query = from t1 in db.Table1
join t2 in db.Table2 on t1.Id equals t2.t1Id into joined
from j in joined.DefaultIfEmpty()
where j == null
select t1;
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.