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--- v5:dictionary:structure:addattribute [2016/04/09 18:39] – mnewnham
+++ v5:dictionary:structure:addattribute [2016/04/10 02:41] (current) – mnewnham
@@ Line 13: / Line 13: @@
       )
 </WRAP>
-The method ''addAttribute()'' is part of the **//Structured Schema Management//** suite, and adds an attribute to the current [[v5:dictionary:stucture:metaobjectstructure|metaObjectStructure]] object.
+The method ''addAttribute()'' is part of the **//Structured Schema Management//** suite, and adds an attribute to the current metaObjectStructure object.
 An attribute can be added to any of the available structure types, table,column,index or index-item.
@@ Line 48: / Line 48: @@
   ->addAttribute(array('TABLESPACE'=>'LARGE1'),'db2');
 </code>
-<WRAP clear />
+===== Understanding Attributes =====
+==== Portable Attributes ====
+Portable attributes are comparable to the options available to the original [[v5:dictionary:column_attributes|Column Attributes]] in **//Simple Schema Management//**.
+  * If a feature is **portable**, no platform designation is generally necessary but can still be used
+  * Portable options may have a **//priority//** automatically assigned, which may control the order of definitions. In particular, the priority will force the NOTNULL and DEFAULT attributes to conform to the ANSI SQL order.
+==== Non-Portable (Custom) Attributes ====
+A custom attribute is one that must be defined fully in order to be handled correctly by the DBMS. In principle, any option not all ready defined as portable in the [[v5:dictionary:column_attributes|Column Attributes]] list is a custom attribute.
+In the following example, we create a column, and add 3 attributes to it. 1 attribute is portable and 2 are custom.
+<code php>
+/*
+* We define a metaObjectStructure, that represents
+* the table 'employees'
+*/
+$dict = NewDataDictionary($db);
+$t = new metaObjectStructure($dict,'employees');
+/*
+* We now add an object representing the column, 'somecolumn' of type Character(32)
+*/
+$c = $t->addColumnObject('somecolumn','C(32)');
+/*
+* now add a portable attribute DEFAULT
+* This could also be passed as a string "DEFAULT 'SOMEVALUE'")
+*/
+$c->addAttribute(array('DEFAULT'=>'SOMEVALUE');
+/*
+* now add a custom attribute to column, applicable to all platforms
+*/
+$c->addAttribute(array('CHARACTER SET'=>'"ascii"'));
+/*
+* Now add another attribute, which is only used if the database type is SQL Server
+*/
+$c->addAttribute('SPARSE','mssqlnative');
+/*
+* This object is now passed to the addColumnSql method
+*/
+$sql = $dict->addColumnSql($t)
+</code>
+If ADOdb was attached to a MySQL database, the sql returned would be:
+  ALTER TABLE employees ADD somecolumn VARCHAR(32)
+                             DEFAULT 'SOME VALUE'
+                             CHARACTER SET "ascii"
+but if attached to a SQL Server database, it would appear as:
+  ALTER TABLE employees ADD somecolumn VARCHAR(32)
+                            DEFAULT "SOME VALUE"
+                      CHARACTER SET "ascii"
+                             SPARSE