Advanced for simple. data, advanced for simple. data

Advanced for simple. data, advanced for simple. data

I. sorting results

-OrderBy (ascending)

-OrderByDescending (in descending order)

db.Product.All().OrderByFactoryName();db.Product.All().OrderByFactoryNameDescending();

Or

db.Product.All().OrderBy(db.Product.FactoryName);db.Product.All().OrderByDescending(db.Product.FactoryName);

Ii. Table join

1. No foreign key constraints

1.1 natural connections

-Join

-Left Join

-Outer Join

var q = _db.Order.Query().Join(_db.OrderDetail, ).Where(_db.OrderDetail.UnitPrice > 15000);List<dynamic> employees = q.Select(_db.Order.OrderCode, q.OrderDetail.CategoryName).ToList();

1.2 cascading Query

-

-WithOne

-WithMany

dynamic OrderDetailAlias;var OrderDetails = db.Order.All().With(db.Order.OrderDetail.As("OrderDetailInfo"), out OrderDetailAlias) 
.Select( db.Order.OrderCode, BandAlias.Name);

 

 

2. Foreign key constraints

2.1. A single dataset is returned

var orders = _db.Order.FindAllByCustomerId(10).Select(_db.Order.OrderCode, q.Order.OrderDetail.CategoryName);

(Using the foreign key of the database)

 

var orders = _db.Order.FindAllByCustomerId(10).Select(_db.Order.OrderCode, _db.OrderDetail.CategoryName).Join(_db.OrderDetail).On(OrderId: _db.Order.PKID);

(Replace foreign key)

var orders = _db.Order.FindAllByCustomerId(10).Select(_db["Order"]["OrderCode"], _db["OrderDetail"]["CategoryName"]).Join(_db["OrderDetail"]).On(OrderId: _db["Order"]["PKID"]);

(Replace foreign key-index writing)

Iii. Aggregate functions

1. Having

var orderDetails= db.OrderDetail.All().Select(db.OrderDetail.Order.OrderCode,         db.OrderDetail.PKID.Count().As("OrderDetailCount")).Having(db.OrderDetail.PKID.Count() > 2);

 

2. Max, Min, Sum, Count, and Avg

var orderDetails=db.OrderDetail.All().Having(db.OrderDetail.UnitPrice.Max()>100);

var orderDetails=db.OrderDetail.All().Having(db.OrderDetail.UnitPrice.Min()>100);

3. Count, CountDistinct

Var orderDetails = db. orderDetail. all (). select (db. orderDetail. orderId. count (); var orderDetails = db. orderDetail. all (). select (db. orderDetail. orderId. countDistinct (); deduplication count

 

Iv. Help Functions

1. Length (field Length)

var codeLength=db.Order.Select(db.Order.OrderCode.Length().As("CodeLength"));

2. Convert to Scalar Value

2.1. ToScalar and ToScalar <T> return an attribute as the scalar value from the query results.

int id=db.Order.Get(1).ToScalar();int id=db.Order.Select(db.Order.Id).Get(1).ToScalar();

 

2.2. ToScalarOrDefault and ToScalarOrDefault <T> return an attribute from the query result as the scalar value, which is the default value. If the attribute value is NULL, ToScalarOrDefault <T> Returns default <T>

string orderCode=db.Order.FindAllById(1).Select(db.Order.OrderCode).ToScalarOrDefault();

 

2.3. ToScalarList and ToScalarList <T> return a list from a series of query results as scalar values.

List<string> orderDetails=db.OrderDetail.FindAllByOrderId(1).Select(db.OrderDetail.CategoryName).ToScalarList<string>();

 

2.4. ToScalarArray and ToScalarArray <T> return an array as the scalar value from a series of query results.

string[] orderDetails=db.OrderDetail.FindAllByOrderId(1).Select(db.OrderDetail.CategoryName).ToScalarArray<string>();

 

To be continued...

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