ADOdb

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Adding Comments To Tables

Database support for adding comments varies from full support (IBM DB2, PostgreSQL) to none (SQLite) with differing implementation methods. Databases that support it do it via 1 of 2 methods, Either be adding the comment as part of the table creation and modification process, or by adding a comment to a previously created table. In addition, databases have varying levels of support for adding comments to tables, columns and indexes. The following matrix shows available methods across supported databases.

	db2	mssqlnative	mysql	oci8	postgres9
Table On Creation			YES
Column On Creation			YES
Index On Creation			YES
Table After Creation	YES	YES		YES	YES
Column After Creation	YES	YES		YES	YES
Index After Creation	YES	YES			YES

Creating Comments During Table Creation

Creation during data dictionary functions such as createTableSql(), addColumnSql() are built as follows:

Table

$datadict = newDataDictionary($db);
 
$flds = 'an ADOdb fields definition...';
$tableOpts = ['COMMENT' => 'This is a table Comment' ];
 
$sqlarray = $datadict->createTableSql('some_table',$flds, $tableopts);
 
$datadict->executeSqlArray($sqlArray);

Column

$datadict = newDataDictionary($db);
 
$flds = "SOME_FIELD C(60) NOTNULL COMMENT 'THIS IS A COLUMN COMMENT'";
 
$sqlarray = $datadit->alterColumnSql('some_table',$flds);
 
$datadict->executeSqlArray($sqlArray);

Index

$datadict = newDataDictionary($db);
 
$flds = "VARCHAR_FIELD, DATE_FIELD, INTEGER_FIELD";
$indexOptions = array(
    'UNIQUE',
    'COMMENT' => 'THIS IS AN INDEX COMMENT'
);
 
$sqlarray = $datadict->addIndexSql('some_index', 'some_table',$flds, $indexopts);
 
$datadict->executeSqlArray($sqlArray);

Creating Comments Using XMLSchema

Comments can now be added to table, column and index elements and are added if possible to the database schema. If the database does not support the operation they are ignored.
This is done by adding <comment></comment> as part of the element
The <descr> tag no longer attempts to create comments for tables and columns. Any DESCR tags are used solely as XML descriptions.

<table name="xml_schema_test">
  <descr>A test table for xmlschema unit testing</descr>
  <comment>XML SCHEMA COMMENT</comment> 
  <field name="id" type="I">
  <descr>A unique ID assigned to each record.</descr>
  <KEY/>
  <AUTOINCREMENT/>
  <comment>This is a column comment</comment>
  </field> 
  <index name="index1">
     <col>id</col>
     <comment>This is an index comment</comment>
  </index>
</table>

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