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--- dictionary:index [2015/08/12 01:58] – [Using Data Types For Non-Portable Applications] mnewnham
+++ dictionary:index [2015/08/14 00:55] (current) – removed mnewnham
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-====== The Data Dictionary ======
-===== Introduction =====
-The Data Dictionary provides a series of functions **'Meta-Functions'** that allow a portable method of managing the schema of databases, from simple querying of data attributes of columns to XML based routines to build and manage new tables.
-===== Portable Data Types =====
-ADOdb provides a cross-platform method of identifying the data type of a field. These values can be used as a replacement in code that relies on the data type of field to produce a result. Each database driver contains a cross-reference table of datatypes that can accessed using the [[reference:metatype|metaType()]] method.
-==== Summary Of Types ====
-^Type^Represents Field Types^
-|C|character fields that should be shown in a <input type="text"> tag|
-|X|TeXt, large text fields that should be shown in a <textarea>|
-|B|Blobs, or Binary Large Objects. Typically images.|
-|D|Date field|
-|T|Timestamp field|
-|L|Logical field (boolean or bit-field). Some databases emulate logicals using I2 fields|
-|I|Integer field, This may be broken down further into I2,I4 or I8 types|
-|N|Numeric field. Includes autoincrement, numeric, floating point, real and integer.|
-|R|Serial field. Includes serial, autoincrement integers. This works for selected databases. Some databases do not signify if a field is auto-increment|
-==== Using Data Types For Non-Portable Applications ====
-There are benefits to using ADOdb data types even when writing an application that is not designed to be portable. The ''metaType()'' method can hide numerous data sub-types from a developer, when the difference in the field is not important. For example the following actual data types in the [[database:Microsoft SQL Server]] driver are all represented by the ADOdb type ''C'':
-^Data Type^Description^
-|-9|nvarchar|
-|-8|nchar|
-|1|char|
-|12|varchar|
-===== The Meta Functions =====
-Metadata functions convert database specific table, column and index queries into a standardized cross-database format.
-| [[dictionary:MetaColumns|metaColumns()]]          | Returns a list of available columns and column type information for the supplied table name  |
-| [[dictionary:MetaColumnNames|metaColumnNames()]]  | Returns a list of available columns for the supplied table name                              |
-| [[dictionary:metadatabases|metaDatabases()]]      | Returns a list of available databases                                                        |
-| [[dictionary:MetaForeignKeys|metaForeignKeys()]]  | Returns a list of foreign keys for the supplied table name                                   |
-| [[dictionary:metaindexes|metaIndexes()]]          | Returns a list of indexes for the supplied table name                                        |
-| [[dictionary:MetaPrimaryKeys|metaPrimaryKeys()]]  | Returns a list of primary keys for the supplied table name                                   |
-| [[dictionary:MetaProcedures|metaProcedures()]]    | Returns a list of procedures and functions for the connected database                        |
-| [[dictionary:MetaTables|metaTables()]]            | Returns list of available tables for the supplied database name                              |
-| [[dictionary:metatype|metaType()]]                | Converts database-specific data type into a portable type                                    |
-| [[dictionary:serverinfo|serverInfo()]]            | Returns a set of server information                                                          |
-===== Managing Tables And Columns =====
-===== Managing Indexes =====
-===== XML Driven Functions =====