Mego开发文档 - 复杂查询

Posted 2020-10-30 CarefreeXT

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复杂查询

Mego 还支持一些更高级的LLINQ查询写法，本文只列出一部分。

分组汇总查询

            using (var db = new OrderManageEntities())
            {
                var query = from a in db.Products
                            group a by a.Category into g
                            select new
                            {
                                g.Key,
                                Count = g.Count(),
                                Max = g.Max(a => a.Id)
                            };
                var data = query.ToArray();
            }

分组查询及分页

using (var db = new OrderManageEntities())
{
    var query = (from a in db.Products
                 group a by a.Category into g
                 select new
                 {
                     g.Key,
                     List = g
                 })
                 .Skip(2).Take(2);
    var data = query.ToArray();
}

连接分组查询

using (var db = new OrderManageEntities())
{
    var query = from a in db.Orders
                join b in db.OrderDetails on a.Id equals b.OrderId into g
                select new
                {
                    Order = a,
                    MaxId = g.Max(m => m.Id)
                };
    var data = query.ToArray();
}

连接分组查询及分页

using (var db = new OrderManageEntities())
{
    var query = (from a in db.Orders
                 join b in db.OrderDetails on a.Id equals b.OrderId into g
                 select new
                 {
                     Order = a,
                     List = g
                 })
                 .Skip(5).Take(5);
    var data = query.ToArray();
}

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