[英]How to convert from PostgreSQL query to LINQ or lambda expression
I have a PostgreSQL query that I need to convert to Lamba exp or LINQ to use in my ASP.NET Core C# project.我有一个 PostgreSQL 查询,我需要将其转换为 Lamba exp 或 LINQ 以在我的 ASP.NET Core C# 项目中使用。 Furthermore, the name of the table is "DeliveryFinances".此外,表的名称是“DeliveryFinances”。
This is my PostgreSQL query这是我的 PostgreSQL 查询
SELECT t1."DriverId", t2."OrderNo", COUNT(*)
FROM public."DeliveryFinances" t1
JOIN
(
SELECT MIN("OrderNo") AS "OrderNo", "DriverId"
FROM public."DeliveryFinances"
GROUP BY "DriverId"
) t2 ON t1."DriverId" = t2."DriverId"
GROUP BY t1."DriverId", t2."OrderNo"
LIMIT 25
This is the result I get after running the query in pgAdmin这是我在 pgAdmin 中运行查询后得到的结果
| DriverId| OrderNo | count |
|----------------------------
| 123123 | REQWFA | 3|
| 345534 | ASDCA3 | 2|
| 565534 | MCJSL1 | 1|
Is there any way that I can do this in lambda or LINQ?有什么办法可以在 lambda 或 LINQ 中做到这一点吗? Please help me.请帮我。
Using EF Core 5, a straight forward translation seems to work:使用 EF Core 5,直接翻译似乎有效:
var qmin = from t2 in DeliveryFinances
group t2.OrderNo by t2.DriverId into dg
select new { OrderNo = dg.Min(), DriverId = dg.Key };
var q = from t1 in DeliveryFinances
join t2 in qmin on t1.DriverId equals t2.DriverId
group new { t1, t2 } by new { t1.DriverId, t2.OrderNo } into t1t2g
select new {
t1t2g.Key.DriverId,
t1t2g.Key.OrderNo,
Count = t1t2g.Count()
};
var ans = q.Take(25);
It did not seem particularly efficient on my database, but translated pretty much directly to your SQL.它在我的数据库上似乎不是特别有效,但几乎直接转换为您的 SQL。
A better look at your data might provide a way to use a Group Join in the query, but it might not be translatable to SQL.更好地查看您的数据可能会提供一种在查询中使用 Group Join 的方法,但它可能无法转换为 SQL。
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