Using Caché Objects - InterSystems Documentation

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Objects and SQL • All the columns in the projection of the superclass (that is, those based on all the properties in its superclass' extent) • Additional columns based on properties only in the subclass • A subset of the rows in the superclass' table that consists only of the instances of the subclass For example, the projection of a persistent class called Sample.Employee that is derived from the Sample.Person class is a table containing all the fields defined by both the Sample.Employee and Sample.Person classes. This is illustrated in the following SQL queries. First list all instances of Sample.Person and its properties: SELECT * FROM Sample.Person Now list all instances of Sample.Employee and its properties: SELECT * FROM Sample.Employee Typically, the table of a subclass has more columns and fewer rows than its parent. There are more columns in the subclass since it usually adds additional properties when it extends the parent class; there are often fewer rows since there are often fewer instances of the subclass than the parent. 13.1.1 How a Class is Projected to SQL To create a class that is automatically accessible from SQL, define it based on the %Persistent. When you compile the class, the Caché Class Compiler automatically generates the runtime information needed for relational access. The class' instances are then available as the rows of a relational table. 13.1.2 Naming Rules for Projected Classes Caché itself places no restrictions on class names. However, SQL tables cannot have names that are SQL Reserved Words; hence, if you create a persistent class with a name that is a reserved word, the Caché Class Compiler will generate an error message. In this case, you must either rename the class or specify a table name for the projection that differs from the class name; to do this, use the SQLTABLENAME keyword, which has the following syntax: SQLTABLENAME = TableNameForSQL; 114 Using Caché Objects
The Object-SQL Projection 13.2 The Object-SQL Projection This section describes the manner in which the various elements of a class are projected from an object-based form to one that is SQL-based. Fundamentally, a persistent Caché class is projected to a unique SQL table, where each of its instances is projected as a row within that table. Other items are projected as listed below. The Object-SQL Projection From (Object Concept)... Package Class OID Data type property Reference property Embedded object List property Array property Stream property Index Method To (Relational Concept)... Schema Table Identity field Field Reference field Set of Fields List field Child table BLOB Index Stored procedure (class methods only) See the appropriate section below for more information on each individual topic. You can also include SQL triggers in your classes; for information on their projection, see the section on SQL Triggers below. 13.2.1 Identity (OIDs Projected to SQL) Each object that inherits from %Persistent is uniquely identified by its OID (object identifier); in the projection, each instance is uniquely identified by the value of its entry in the generated identity (ID) column in the class' table. The value of the instance's entry in the identity column is the same as that of the ID portion of its OID. Using Caché Objects 115
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Using Caché Objects Version 5.2 01
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Table of Contents 1 Introduction to
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7 Properties ......................
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13.1 Inheritance and SQL ..........
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20.8 %OnNew .......................
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List of Figures Embeddable Objects
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1 Introduction to Caché Objects Th
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1.2 Class Definitions and the Class
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Development Tools Caché Class Libr
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• The Caché EJB Binding—a vers
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2 Object-Oriented Database Developm
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Encapsulation Caché exploits inher
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3 The Caché Object Model The Cach
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Referring to an Object — OREF, OI
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Types of Classes 3.2.1 Transient Ob
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Types of Classes Embeddable Objects
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A class inherits all of the specifi
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2. It resolves inheritance—it det
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Caché Classes • Class Parameters
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Caché Classes ClientDataType Descr
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Caché Classes Internally, this wor
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Packages Class Packages Any of thes
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Packages Letting the compiler resol
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Packages • “%Library” —any
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Methods where count and state are d
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Methods 6.4 Method Language You hav
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Methods 6.6 Instance and Class Meth
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Methods Write dog.Speak() Which cou
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Properties 7.1 Property Keywords Yo
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Properties Property Behavior The pr
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Properties 7.5 Attribute Properties
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Properties You can manipulate a col
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8 Class Queries Class queries provi
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Query Basics Final Specifies that s
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Caché ObjectScript. These queries
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The data in Row is the result of ex
Page 75 and 76: 9 Indices Indexes provide a mechani
Page 77 and 78: Index Collation 9.2 Index Collation
Page 79 and 80: 10 Using Objects with Caché Object
Page 81 and 82: Executing Methods 10.1.3 Executing
Page 83 and 84: Opening Objects 10.3 Opening Object
Page 85 and 86: where oref is the OREF of the speci
Page 87 and 88: For example, to populate the Home p
Page 89 and 90: change the second vaccination recor
Page 91 and 92: There are two types of array proper
Page 93 and 94: Saving Objects 10.5 Saving Objects
Page 95 and 96: mation. Again, this method deletes
Page 97 and 98: Set rset = ##class(%ResultSet).%New
Page 99: Executing Queries // Create a Resul
Page 102 and 103: Data Types 11.1 Available Types Cac
Page 104 and 105: Data Types • INDEXSUBSCRIPTS —
Page 106 and 107: Data Types CLIENTDATATYPE Values Va
Page 108 and 109: Data Types SQLCATEGORY Values Value
Page 110 and 111: Data Types The property is restrict
Page 112 and 113: Object Persistence 1. Its primary (
Page 114 and 115: Object Persistence Note: In a multi
Page 116 and 117: Object Persistence // Open person "
Page 118 and 119: Object Persistence For example: //
Page 120 and 121: Object Persistence If a persistent
Page 122 and 123: Object Persistence The storage clas
Page 125: 13 Objects and SQL A key aspect of
Page 129 and 130: The Object-SQL Projection 13.2.2.1
Page 131 and 132: The Object-SQL Projection • The p
Page 133 and 134: If the list for a particular instan
Page 135 and 136: Triggers are, however, fired by the
Page 137 and 138: 14 Relationships A relationship is
Page 139 and 140: Relationship Basics the relationshi
Page 141 and 142: An Invoice class class MyApp.Invoic
Page 143: 14.4 Persistent Behavior of Relatio
Page 146 and 147: Streams Stream data may be stored i
Page 148 and 149: Streams 15.2.2 Copying Data between
Page 150 and 151: Streams Set stream=##class(%Stream.
Page 153 and 154: 16 Class Projections Class projecti
Page 155 and 156: RemoveProjection The RemoveProjecti
Page 157 and 158: 17 Object Synchronization Object sy
Page 159 and 160: About Updates • If two changes re
Page 161 and 162: About Updates Two Synchronized Data
Page 163 and 164: • classname is a quoted string th
Page 165 and 166: Set Status = TargetSyncSet.Import(f
Page 167 and 168: 18 Method Generators A powerful fea
Page 169 and 170: Method Generator Context 6. It copi
Page 171: Implementing Method Generators 3. A
Page 174 and 175: The Caché Data Population Utility
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The Caché Data Population Utility
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Using Callback Methods Since differ
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Using Callback Methods ReturnValue
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Using Callback Methods 20.6 %OnDele
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Using Callback Methods 20.10 %OnRol
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21 Object-Specific ObjectScript Fea
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##this Syntax >Do ##class(Package.C
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##super Syntax 21.4 ##super Syntax
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You can override a property's defau
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Dynamic Dispatch 22.2 Content of Me
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Dynamic Dispatch %DispatchMethod ca
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23 Class Definition Classes The Cac
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You can get detailed information ab
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Internet Classes addressed to , its
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Internet Classes For more informati
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Object Concurrency Setting 1 2 3 4
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Object Concurrency Note: You can us
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