/ doc / tocInheritance / CompoundKey / __TOCDet / Description

Description

Edit keys at this level only

= A class able to expand the concept of entity keys.0x000D0x000A0x000D0x000AExample: In addition to ordinary keys for 'Customer' like 'FirstName', 'LastName' and 'DateOfBirth', it is able to offer:0x000D0x000A1) Expressions like "FirstName'+' '+'LastName" (see -BinaryOperatorKey- and -ConstantKey-).0x000D0x000A2) Keys implemented directly in actual class like 'Name' (see -EntityMethodKey-).0x000D0x000A3) Functions acting on keys, like 'DateOfBirth.Year()' (see -FunctionKey- / -FunctionKeyYear-).0x000D0x000A4) Global new keys like 'CountP()' (see -NewKey- / -NewKeyCountP-).0x000D0x000A5) Foreign keys with for instance aggregations like 'Order.Amount.Sum()' (see -ForeignKey- / -FunctionKeyAggregate- / -FunctionKeyAggregateSum).0x000D0x000A0x000D0x000AThese keys / expressions can then be used whenever ordinary keys are used, like in -QueryExpression-s like SELECT, WHERE, AGGREGATE, PIVOT and so on.0x000D0x000A0x000D0x000AMost relevant sub classes of -CompoundKey- are:0x000D0x000A0x000D0x000A1) -BinaryOperatorKey-: Offers expressions with operators like +, -, * and /.0x000D0x000A0x000D0x000A2) -ConstantKey-: Represents a constant expression like "' '", "', '", "42".0x000D0x000A0x000D0x000A3) -EntityMethodKey-: Key able to call read-only methods defined in the entity class with names like 'TryGet0x007BFieldName0x007D'.0x000D0x000AExample: For 'Customer' it can find 'Customer.Name' which is calculated in a read-only method Customer.TryGetName as combination of 'FirstName', 'LastName' and 'CompanyName'.0x000D0x000A0x000D0x000A4) -NewKey-: Creates new keys available for all entities.0x000D0x000AExample: For 'Customer' it can count number of properties through 'CountP' (see -NewKeyCountP-.)0x000D0x000A0x000D0x000A5) -ForeignKey-: Can find related values.0x000D0x000AExample: For 'Order', it can find 'Customer.Name'.0x000D0x000A0x000D0x000A6) -MemberEntityKey-: Can find value for entity which is member of entity being queried.0x000D0x000AExample: For 'Order', it can find 'Customer.Name'.0x000D0x000A0x000D0x000AClosely related classes (Stored inside -CompoundKey- as members -FunctionKeys-, and -QuantileKey-) are:0x000D0x000A1) -FunctionKey- / -FunctionKeyAggregate-: Extracts data from an already existing value like 'Created.Year()' (see -FunctionKeyYear-)0x000D0x000Aand0x000D0x000A2) -QuantileKey-: Can separate entities into quantiles, like Quartiles, Quintiles or Sextiles0x000D0x000A0x000D0x000A(See also -ValueComparer- which can evaluation expressions like for 'Customer': 'WHERE Created = ThisYear')0x000D0x000A0x000D0x000AOther sub-classes of -CompoundKey- are -OrdinaryKeyPlusFunctionOrQuantile- and -CompoundInvalidKey-.0x000D0x000A0x000D0x000ASee common parser for all compound keys (-Parse-) which will always 'succeed' (a 'TryParse'-method is neither needed nor offered, -CompoundInvalidKey- is returned if not key found).0x000D0x000A0x000D0x000ANote how compound keys (and related keys) may be chained several levels deep, like for 'Order': 'Customer.Created.Year()' or for 'Customer': 'Order.Amount.Sum()' or even 'Order.Amount.Sum().QUARTILE'.0x000D0x000AThis is all parsed in -Parse- and stored in -FunctionKeys- / -QuantileKey-.0x000D0x000A0x000D0x000ASee -QueryExpressionSelect- for hint about using 'AS'-clause in order to simplify parsing and evaluation in subsequent -QueryExpression-s when using -CompoundKey-.0x000D0x000A0x000D0x000AAll keys can be followed by one or several -FunctionKey-s0x000D0x000A0x000D0x000AA -QuantileKey- can only be the last key in a chain, like 'Customer.Order.Amount.Sum().QUARTILE'.0x000D0x000AIt is not evaluated by -CompoundKey-.-TryGetP-, it is instead evaluated by -ARCQuery-. -Extensions-.-TryGetP-)0x000D0x000A0x000D0x000A

Edit keys at all sub levels.
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