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Reverse Module

Reverse Module -- Module for managing database structure


The Reverse module is an extension of the Common Module driver, and is made up in the following structure:


In order to use the MDB2 Reverse drivers, it is necessary to first load the Reverse driver into your MDB2 instance. Let's start a MDB2 instance and set up our connection:
In the above example, we have created a valid connection to a database that does exist, using a valid user and password for our database server. We now have access to all of the MDB2 Reverse functionality within our example application. For the purposes of this document, we will set up an example table as such:

getTableFieldDefinition() Method

The getTableFieldDefinition() Method exists primarily to get an array that defines a table field. This array can then be used to re-create the table elsewhere, or for any other purpose that may be necessary. Using the MDB2 instance defined above, we will connect to a database, define a table that we want to work with, and reverse engineer a specific field that we are interested in. First, we need to define the table and field that we want to work with; then, it is as easy as a single line of code to get the table definition back as an array of mixed values, then using var_dump to view the results:
The return will look something like the following, depending on your field definition:
array(1) {
  [0] => array(5) {
    ['notnull'] => bool(false)
    ['nativetype'] => string(4) "date"
    ['default'] => NULL
    ['type'] => string(4) "date"
    ['mdb2type'] => string(4) "date"

Additional table information

A number of other methods exist to gain information about a selected table. You may use any of the following methods according to the information needed:

tableInfo() Method

This method will return a lot of information regarding a table, and can be used in a number of different ways. The information that it returns will differ slightly across different RDBM's and may give some variance in results. This method can be used to query either a table definition, or a resultset, which makes it great for creating optimized tables. The tableInfo() method allows you to pass a parameter for the mode that you would like to see the results presented as. In order to demonstrate the results more effectively, we will use a series of examples to do some queries and return the results in different modes. NOTE: Either a table OR a resultset can be passed as the first parameter to get information on the table. In these examples, we will be using the table that we defined above.
In the subsequent examples, we will only include the first table field definition, as it effectively illustrates the differences in modes. Now, let's change the mode to MDB2_TABLEINFO_ORDER. In addition to the information found in the default output, a notation of the number of columns is provided by the num_fields element while the order element provides an array with the column names as the keys and their location index number (corresponding to the keys in the default output) as the values.
Changing the mode to MDB2_TABLEINFO_ORDERTABLE will give us some additional information by adding additional dimensions to the array in which the table names are keys, and the field names are sub keys. This type of query can be useful when querying complex joins, where some field names may be the same.

NOTE: The flags element will contain a space-separated list of additional information about the field. This data is inconsistent between RDBMS's due to the way each RDBMS works:

Most RDBMS's only provide the table and flags elements if the result is a table name. If the portability option is set to MDB2_PORTABILITY_FIX_CASE, the names of tables and fields will be lower- or upper-cased. If the case is set to CASE_UPPER all tables and fields will be uppercased, as is seen in Oracle and Firebird/Interbase, while CASE_LOWER will lower case all field and table names; this is the default setting.

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