path: root/doc/ref-ooddl.xml

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<!-- Object Oriented Data Definition Language -->
<reference id="ref-ooddl">
  <title>Object Oriented Data Definition Language (OODDL)</title>
  <partintro>
    <para>
      The Object Oriented Data Definition Language (OODDL) provides
      access to relational SQL tables using Common Lisp Object System
      (CLOS) objects.  SQL tables are mapped to CLOS objects with the
      SQL columns being mapped to slots of the CLOS object.
    </para>
    <para>
      The mapping between SQL tables and CLOS objects is defined with
      the macro <link
      linkend="def-view-class"><function>def-view-class</function></link>. SQL
      tables are created with <link
      linkend="create-view-from-class"><function>create-view-from-class</function></link>
      and SQL tables can be deleted with <link
      linkend="drop-view-from-class"><function>drop-view-from-class</function></link>.
    </para>
    <note>
      <para>The above functions refer to the Lisp
      <emphasis>view</emphasis> of the SQL table. This Lisp view
      should not be confused with SQL <function>VIEW</function>
      statement.</para>
    </note>
  </partintro>

  <refentry id="standard-db-object">
    <refnamediv>
      <refname>STANDARD-DB-OBJECT</refname>
      <refpurpose>Superclass for all &clsql; View Classes.</refpurpose>
      <refclass>Class</refclass>
    </refnamediv>
    <refsect1>
      <title>Class Precedence List</title>
      <para>
	<simplelist type="inline">
	  <member><type>standard-db-object</type></member>
	  <member><type>standard-object</type></member>
	  <member><type>t</type></member>
	</simplelist>
      </para>
    </refsect1>
    <refsect1>
      <title>Description</title> <para>This class is the superclass
      of all &clsql; View Classes.</para>
    </refsect1>
    <refsect1>
      <title>Class details</title>
      <programlisting>(defclass STANDARD-DB-OBJECT ()(...))</programlisting>
    </refsect1>
    <refsect1>
      <title>Slots</title>
      <para>
	<simplelist>
	  <member>slot VIEW-DATABASE is of type (OR NULL DATABASE)
	  which stores the associated database for the
	  instance.</member>
	</simplelist>
      </para>
    </refsect1>
  </refentry>

  <refentry id="default-string-length">
    <refnamediv>
      <refname>*DEFAULT-STRING-LENGTH*</refname>
      <refpurpose>Default length of SQL strings.</refpurpose>
      <refclass>Variable</refclass>
    </refnamediv>
    <refsect1>
      <title>Value Type</title>
      <para>
	Fixnum
      </para>
    </refsect1>
    <refsect1>
      <title>Initial Value</title>
      <para><parameter>255</parameter></para>
    </refsect1>
    <refsect1>
      <title>Description</title>
      <para>
	If a slot of a class defined by
	<function>def-view-class</function> is of the type
	<parameter>string</parameter> or
	<parameter>varchar</parameter> and does not have a length
	specified, then the value of this variable is used as SQL
	length.
      </para>
    </refsect1>
    <refsect1>
      <title>Examples</title>
      <screen>
(let ((*default-string-length* 80))
  (def-view-class s80 ()
    ((a :type string)
     (b :type (string 80))
     (c :type varchar))))
=> #&lt;Standard-Db-Class S80 {480A431D}>

(create-view-from-class 's80)
=>
(table-exists-p [s80])
=> T
      </screen>
      <para>
	The above code causes a SQL table to be created with the SQL command
      </para>
      <screen>CREATE TABLE (A VARCHAR(80), B CHAR(80), C VARCHAR(80))</screen>
    </refsect1>
    <refsect1>
      <title>Affected By</title>
      <para>
        Some SQL backends do not support
        <parameter>varchar</parameter> lengths greater than 255.
      </para>
    </refsect1>
    <refsect1>
      <title>See Also</title>
      <para>None.</para>
    </refsect1>
    <refsect1>
      <title>Notes</title>
      <para>This is a CLSQL extension to the CommonSQL API.</para>
    </refsect1>
  </refentry>

  <refentry id="create-view-from-class">
    <refnamediv>
      <refname>CREATE-VIEW-FROM-CLASS</refname>
      <refpurpose>Create a SQL table from a <glossterm linkend="gloss-view-class">View Class</glossterm>.</refpurpose>
      <refclass>Function</refclass>
    </refnamediv>
    <refsect1>
      <title>Syntax</title>
      <synopsis>
      <function>create-view-from-class</function> <replaceable>view-class-name</replaceable> &amp;key <replaceable>database</replaceable> <replaceable>transactions</replaceable> => <returnvalue><!-- no values --></returnvalue></synopsis>
    </refsect1>
    <refsect1>
      <title>Arguments and Values</title>
      <variablelist>
	<varlistentry>
	  <term><parameter>view-class-name</parameter></term>
	  <listitem>
	    <para>
	      The name of a <glossterm linkend="gloss-view-class">View
	      Class</glossterm> that has been defined with <link
	      linkend="def-view-class"><function>def-view-class</function></link>.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><parameter>database</parameter></term>
	  <listitem>
	    <para>
	      The <glossterm
	      linkend="gloss-database-object">database</glossterm> in
	      which to create the SQL table. This will default to the
	      value of <symbol>*default-database*</symbol>.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><parameter>transactions</parameter></term>
	  <listitem>
	    <para>
	      When &nil; specifies that a table type which does not
	      support transactions should be used.
	    </para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </refsect1>
    <refsect1>
      <title>Description</title>
      <para>
	Creates a table as defined by the <glossterm
	linkend="gloss-view-class">View Class</glossterm>
	<parameter>view-class-name</parameter> in
	<parameter>database</parameter>.
      </para>
    </refsect1>
    <refsect1>
      <title>Examples</title>
      <screen>
(def-view-class foo () ((a :type (string 80))))
=> #&lt;Standard-Db-Class FOO {4807F7CD}>
(create-view-from-class 'foo)
=>
(list-tables)
=> ("FOO")
      </screen>
    </refsect1>
    <refsect1>
      <title>Side Effects</title>
      <para>
	Causes a table to be created in the SQL database.
      </para>
    </refsect1>
    <refsect1>
      <title>Affected by</title>
      <para>
	Most SQL database systems will signal an error if a table
	creation is attempted when a table with the same name already
	exists. The SQL user, as specified in the database connection,
	must have sufficient permission for table creation.
      </para>
    </refsect1>
    <refsect1>
      <title>Exceptional Situations</title>
      <para>
	A condition will be signaled if the table can not be created
	in the SQL database.
      </para>
    </refsect1>
    <refsect1>
      <title>See Also</title>
      <para>
	<simplelist>
	  <member><link linkend="def-view-class"><function>def-view-class</function></link></member>
	  <member><link linkend="drop-view-from-class"><function>drop-view-from-class</function></link></member>
	</simplelist>
      </para>
    </refsect1>
    <refsect1>
      <title>Notes</title>
      <para>
	Currently, only &mysql; supports transactionless
	tables. &clsql; provides the ability to create such tables for
	applications which would benefit from faster table access and
	do not require transaction support.
      </para>
      <para>
	The case of the table name is determined by the type of the
	database. &mysql;, for example, creates databases in upper-case
	while &postgresql; uses lowercase.
      </para>
    </refsect1>
  </refentry>

  <refentry id="def-view-class">
    <refnamediv>
      <refname>DEF-VIEW-CLASS</refname>
      <refpurpose>Defines CLOS classes with mapping to SQL database.</refpurpose>
      <refclass>Macro</refclass>
    </refnamediv>
    <refsect1>
      <title>Syntax</title>
      <synopsis>
      <function>def-view-class</function> <replaceable>name</replaceable> <replaceable>superclasses</replaceable> <replaceable>slots</replaceable> &amp;rest <replaceable>class-options</replaceable> => <returnvalue>class</returnvalue></synopsis>
    </refsect1>
    <refsect1>
      <title>Arguments and Values</title>
      <variablelist>
	<varlistentry>
	  <term><parameter>name</parameter></term>
	  <listitem>
	    <para>
	      The class name.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><parameter>superclasses</parameter></term>
	  <listitem>
	    <para>
	      The superclasses for the defined class.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><parameter>slots</parameter></term>
	  <listitem>
	    <para>
	      The class slot definitions.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><parameter>class options</parameter></term>
	  <listitem>
	    <para>
	      The class options.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><parameter>class</parameter></term>
	  <listitem>
	    <para>
	      The defined class.
	    </para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </refsect1>
    <refsect1>
      <title>Slot Options</title>
      <itemizedlist>
	<listitem>
	  <para>
	    <parameter>:db-kind</parameter> - specifies the kind of
	    database mapping which is performed for this slot and
	    defaults to <parameter>:base</parameter> which indicates
	    that the slot maps to an ordinary column of the database
	    table. A <parameter>:db-kind</parameter> value of
	    <parameter>:key</parameter> indicates that this slot is a
	    special kind of <parameter>:base</parameter> slot which
	    maps onto a column which is one of the unique keys for the
	    database table, the value <parameter>:join</parameter>
	    indicates this slot represents a join onto another
	    <glossterm linkend="gloss-view-class">View Class</glossterm>
	    which contains View Class objects, and the value
	    <parameter>:virtual</parameter> indicates a standard CLOS
	    slot which does not map onto columns of the database
	    table.
	  </para>
	</listitem>
	<listitem>
	  <para>
	    <parameter>:db-info</parameter> - if a slot is specified
	    with <parameter>:db-kind</parameter>
	    <parameter>:join</parameter>, the slot option
	    <parameter>:db-info</parameter> contains a property list
	    which specifies the nature of the join. The valid members
	    of the list are:
	  </para>
	  <itemizedlist>
	    <listitem>
	      <para>
		<parameter>:join-class</parameter>
		<emphasis>class-name</emphasis> - the name of the
		class to join on.
	      </para>
	    </listitem>
	    <listitem>
	      <para>
		<parameter>:home-key</parameter>
		<emphasis>slot-name</emphasis> - the name of the slot
		of this class for joining
	      </para>
	    </listitem>
	    <listitem>
	      <para>
		<parameter>:foreign-key</parameter>
		<emphasis>slot-name</emphasis> - the name of the slot
		of the <parameter>:join-class</parameter> for joining
	      </para>
	    </listitem>
	    <listitem>
	      <para>
		<parameter>:target-slot</parameter>
		<emphasis>target-slot</emphasis> - this is an optional
		parameter. If specified, then the join slot of the
		defining class will contain instances of this target
		slot rather than of the join class. This can be useful
		when the <parameter>:join-class</parameter> is an
		intermediate class in a
		<emphasis>many-to-many</emphasis> relationship and the
		application is actually interested in the
		<parameter>:target-slot</parameter>.
	      </para>
	    </listitem>
	    <listitem>
	      <para>
		<parameter>:retrieval</parameter>
		<emphasis>time</emphasis> - The default value is
		<parameter>:deferred</parameter>, which defers filling
		this slot until the value is accessed. The other valid
		value is <parameter>:immediate</parameter> which
		performs the SQL query when the instance of the class
		is created. In this case, the
		<parameter>:set</parameter> is automatically set to
		&nil;
	      </para>
	    </listitem>
	    <listitem>
	      <para>
		<parameter>:set</parameter> <emphasis>set</emphasis> -
		This controls what is stored in the join slot.  The
		default value is &t;. When <emphasis>set</emphasis> is
		&t; and <emphasis>target-slot</emphasis> is undefined,
		the join slot will contain a list of instances of the
		join class. Whereas, if
		<emphasis>target-slot</emphasis> is defined, then the
		join slot will contain a list of pairs of
		<emphasis>(target-value join-instance)</emphasis>.
		When <emphasis>set</emphasis> is &nil;, the join slot
		will contain a single instances.
	      </para>
	    </listitem>
	  </itemizedlist>
	</listitem>
	<listitem>
	  <para>
	    <parameter>:type</parameter> - for slots of
	    <parameter>:db-kind</parameter> <parameter>:base</parameter> or
	    <parameter>:key</parameter>, the <parameter>:type</parameter> slot
	    option has a special interpretation such that Lisp
	    types, such as string, integer and float are
	    automatically converted into appropriate SQL types for
	    the column onto which the slot maps. This behaviour may
	    be overridden using the <parameter>:db-type</parameter> slot
	    option. The valid values are:
	    <simplelist>
	      <member>
		<parameter>string</parameter> - a variable length
		character field up to <link
		linkend="default-string-length">*default-string-length*</link>
		characters.
	      </member>
	      <member>
		<parameter>(string n)</parameter> - a fixed length
		character field <parameter>n</parameter> characters
		long.
	      </member>
	      <member>
		<parameter>varchar</parameter> - a variable length
		character field up to <link
		linkend="default-string-length">*default-string-length*</link>
		characters.
	      </member>
	      <member>
		<parameter>(varchar n)</parameter> - a variable length
		character field up to <parameter>n</parameter>
		characters in length.
	      </member>
	      <member>
		<parameter>char</parameter> - a single character field
	      </member>
	      <member><parameter>integer</parameter> - signed integer
	      at least 32-bits wide</member>
	      <member><parameter>(integer n)</parameter></member>
	      <member><parameter>float</parameter></member>
	      <member><parameter>(float n)</parameter></member>
	      <member><parameter>long-float</parameter></member>
	      <member><parameter>number</parameter></member>
	      <member><parameter>(number n)</parameter></member>
	      <member><parameter>(number n p)</parameter></member>
	      <member>
		<parameter>tinyint</parameter> - An integer column 8-bits
		wide. [not supported by all database backends]
	      </member>
	      <member>
		<parameter>smallint</parameter> - An integer column 16-bits
		wide. [not supported by all database backends]
	      </member>
	      <member>
		<parameter>bigint</parameter> - An integer column
		64-bits wide. [not supported by all database backends]
	      </member>
	      <member>
		<parameter>universal-time</parameter> - an integer
		field sufficiently wide to store a
		universal-time. On most databases, a slot of this
		type assigned a SQL type of
		<parameter>BIGINT</parameter>
	      </member>
	      <member>
		<parameter>wall-time</parameter> - a slot which stores
		a date and time in a SQL timestamp column. &clsql;
		provides a number of time manipulation functions to
		support objects of type <type>wall-time</type>.
	      </member>
	      <member>
		<parameter>date</parameter> - a slot which stores the
		date (without any time of day resolution) in a
                column. &clsql; provides a number of time
		manipulation functions that operate on date values.
	      </member>
	      <member>
		<parameter>duration</parameter> - stores a
		<type>duration</type> structure.  &clsql; provides
		routines for <type>wall-time</type> and
		<type>duration</type> processing.
	      </member>
	      <member><parameter>boolean</parameter> - stores a &t; or
	      &nil; value.</member>
	      <member>
		<parameter>generalized-boolean</parameter> - similar
		to a <parameter>boolean</parameter> in that either a
		&t; or &nil; value is stored in the SQL
		database. However, any Lisp object can be stored in
		the Lisp object. A Lisp value of &nil; is stored as
		<constant>FALSE</constant> in the database, any
		other Lisp value is stored as
		<constant>TRUE</constant>.
	      </member>
	      <member>
		<parameter>keyword</parameter> - stores a keyword
	      </member>
	      <member><parameter>symbol</parameter> - stores a symbol</member>
	      <member>
		<parameter>list</parameter> - stores a list by writing
		it to a string. The items in the list must be able to
		be readable written.
	      </member>
	      <member><parameter>vector</parameter> - stores a vector
	      similarly to <parameter>list</parameter></member>
	      <member><parameter>array</parameter> - stores a array
	      similarly to <parameter>list</parameter></member>
	    </simplelist>
	  </para>

	</listitem>
	<listitem>
	  <para>
	    <parameter>:column</parameter> - specifies the name of
	    the SQL column which the slot maps onto, if
	    <parameter>:db-kind</parameter> is not
	    <parameter>:virtual</parameter>, and defaults to the
	    slot name. If the slot name is used for the SQL column
	    name, any hypens in the slot name are converted
	    to underscore characters.
	  </para>
	</listitem>
	<listitem>
	  <para>
	    <parameter>:void-value</parameter> - specifies the value
	    to store in the Lisp instance if the SQL value is NULL and
	    defaults to NIL.
	  </para>
	</listitem>
	<listitem>
	  <para>
	    <parameter>:db-constraints</parameter> - is a keyword
	    symbol representing an SQL column constraint expression or
	    a list of such symbols. The following column constraints
	    are supported: <symbol>:not-null</symbol>,
	    <symbol>:primary-key</symbol>, <symbol>:unique</symbol>,
	    <symbol>:unsigned</symbol> (&mysql; specific),
	    <symbol>:zerofill</symbol> (&mysql; specific) and
	    <symbol>:auto-increment</symbol> (&mysql; specific).
	  </para>
	</listitem>
	<listitem>
	  <para>
	    <parameter>:db-type</parameter> - a string to specify the SQL
	    column type. If specified, this string overrides the SQL
	    column type as computed from the <parameter>:type</parameter>
	    slot value.
	  </para>
	</listitem>
	<listitem>
	  <para>
	    <parameter>:db-reader</parameter> - If a string, then when
	    reading values from the database, the string will be used
	    for a format string, with the only value being the value
	    from the database.  The resulting string will be used as
	    the slot value.  If a function then it will take one
	    argument, the value from the database, and return the
	    value that should be put into the slot. If a symbol, then
	    the symbol-function of the symbol will be used.
          </para>
        </listitem>
	<listitem>
	  <para>
	    <parameter>:db-writer</parameter> - If a string, then when
	    reading values from the slot for the database, the string
	    will be used for a format string, with the only value
	    being the value of the slot.  The resulting string will be
	    used as the column value in the database.  If a function
	    then it will take one argument, the value of the slot, and
	    return the value that should be put into the database. If
	    a symbol, then the symbol-function of the symbol will be
	    used.
          </para>
        </listitem>
      </itemizedlist>
    </refsect1>
    <refsect1>
      <title>Class Options</title>
      <para>
	<itemizedlist>
	  <listitem>
	    <para>
	      <parameter>:base-table</parameter> - specifies the name
	      of the SQL database table. The default value is the
	      class name. Like slot names, hypens in the class name
	      are converted to underscore characters.
	    </para>
	  </listitem>
	  <listitem>
	    <para>
	      <parameter>:normalizedp</parameter> - specifies whether
          this class uses normalized inheritance from parent classes.
          Defaults to nil, i.e. non-normalized schemas. When true,
          SQL database tables that map to this class and parent
          classes are joined on their primary keys to get the full
          set of database columns for this class.  This means that 
          the primary key of the base class will be copied to all 
          subclasses as we insert so that all parent classes of an 
          instance will have the same value in their primary key slots
          (see tests/ds-nodes.lisp and oodml.lisp)
	    </para>
	  </listitem>
	</itemizedlist>
      </para>
    </refsect1>
    <refsect1>
      <title>Description</title>
      <para>
	Creates a <glossterm linkend="gloss-view-class">View
	Class</glossterm> called <parameter>name</parameter> whose
	slots <parameter>slots</parameter> can map onto the attributes
	of a table in a database. If
	<parameter>superclasses</parameter> is &nil; then the
	superclass of <parameter>class</parameter> will be
	<parameter>standard-db-object</parameter>, otherwise
	<parameter>superclasses</parameter> is a list of superclasses
	for <parameter>class</parameter> which must include
	<parameter>standard-db-object</parameter> or a descendent of
	this class.
      </para>

      <refsect2>
      <title>Normalized inheritance schemas</title>
      <para>
    Specifying that <symbol>:normalizedp</symbol> is <symbol>T</symbol>
    tells &clsql; to normalize the database schema for inheritance.
    What this means is shown in the examples below.
      </para>

      <para>
    With <symbol>:normalizedp</symbol> equal to <symbol>NIL</symbol>
    (the default) the class inheritance would result in the following:
      </para>
      <screen>
(def-view-class node ()
  ((title :accessor title :initarg :title :type (varchar 240))))

SQL table NODE:
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| TITLE | varchar(240) | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+

(def-view-class user (node)
  ((user-id :accessor user-id :initarg :user-id
            :type integer :db-kind :key :db-constraints (:not-null))
   (nick :accessor nick :initarg :nick :type (varchar 64))))

SQL table USER:
+---------+--------------+------+-----+---------+-------+
| Field   | Type         | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+-------+
| USER_ID | int(11)      | NO   | PRI |         |       |
| NICK    | varchar(64)  | YES  |     | NULL    |       |
| TITLE   | varchar(240) | YES  |     | NULL    |       |
+---------+--------------+------+-----+---------+-------+
      </screen>

      <para>
    Using <symbol>:normalizedp</symbol> <symbol>T</symbol>, both
    view-classes need a primary key to join them on:
      </para>
      <screen>
(def-view-class node ()
  ((node-id :accessor node-id :initarg :node-id
            :type integer :db-kind :key
            :db-constraints (:not-null))
   (title :accessor title :initarg :title :type (varchar 240))))

SQL table NODE:
+---------+--------------+------+-----+---------+-------+
| Field   | Type         | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+-------+
| NODE_ID | int(11)      | NO   | PRI |         |       |
| TITLE   | varchar(240) | YES  |     | NULL    |       |
+---------+--------------+------+-----+---------+-------+

(def-view-class user (node)
  ((user-id :accessor user-id :initarg :user-id
            :type integer :db-kind :key :db-constraints (:not-null))
   (nick :accessor nick :initarg :nick :type (varchar 64)))
  (:normalizedp t))

SQL table USER:
+---------+-------------+------+-----+---------+-------+
| Field   | Type        | Null | Key | Default | Extra |
+---------+-------------+------+-----+---------+-------+
| USER_ID | int(11)     | NO   | PRI |         |       |
| NICK    | varchar(64) | YES  |     | NULL    |       |
+---------+-------------+------+-----+---------+-------+
      </screen>

      <para>
        In this second case, all slots of the view-class 'node
        are also available in view-class 'user, and can be used
        as one would expect. For example, with the above normalized
        view-classes 'node and 'user, and SQL tracing turned on:
      </para>
      <screen>
CLSQL> (setq test-user (make-instance 'user :node-id 1 :nick "test-user"
                                            :title "This is a test user"))
<![CDATA[#<USER {1003B392E1}>]]>

CLSQL> (update-records-from-instance test-user :database db)
<![CDATA[
;; .. => INSERT INTO NODE (NODE_ID,TITLE) VALUES (1,'This is a test user')
;; .. <= T
;; .. => INSERT INTO USER (USER_ID,NICK) VALUES (1,'test-user')
;; .. <= T
1
]]>

CLSQL> (node-id test-user)
1

CLSQL> (title test-user)
"This is a test user"

CLSQL> (nick test-user)
"test-user"
      </screen>
      <para>
        Notes from a refactor of this code.

        There are many assumptions that need to be met for normalized classes to work

        * The each of the classes should have its own single key column (of a different name)
          that will contain an identical value.  EG: node has a node-id, setting which
          is a node has a node-id and a setting-id which must be equal.  You cannot use
          node-id as the primary key on both tables (as I would have expected).  The exception
          to this seems to be if your class has no slots at all, then you dont need to have a
          single key column, because your class is fully represented in the db by its parent(s)

        * more than one parent class per normalized class should be considered experimental
          and untested (vaya con Dios)

        * There are a few code paths that just dont pay any attention to normalized classes
          eg: delete-records-for-instance

      </para>
      </refsect2>
    </refsect1>
    <refsect1>
      <title>Examples</title>
      <para>
	The following examples are from the &clsql; test suite.
      </para>
      <screen>
(def-view-class person (thing)
  ((height :db-kind :base :accessor height :type float
           :initarg :height)
   (married :db-kind :base :accessor married :type boolean
            :initarg :married)
   (birthday :type clsql:wall-time :initarg :birthday)
   (bd-utime :type clsql:universal-time :initarg :bd-utime)
   (hobby :db-kind :virtual :initarg :hobby :initform nil)))

(def-view-class employee (person)
  ((emplid
    :db-kind :key
    :db-constraints :not-null
    :type integer
    :initarg :emplid)
   (groupid
    :db-kind :key
    :db-constraints :not-null
    :type integer
    :initarg :groupid)
   (first-name
    :accessor first-name
    :type (varchar 30)
    :initarg :first-name)
   (last-name
    :accessor last-name
    :type (varchar 30)
    :initarg :last-name)
   (email
    :accessor employee-email
    :type (varchar 100)
    :initarg :email)
   (ecompanyid
    :type integer
    :initarg :companyid)
   (company
    :accessor employee-company
    :db-kind :join
    :db-info (:join-class company
			  :home-key ecompanyid
			  :foreign-key companyid
			  :set nil))
   (managerid
    :type integer
    :initarg :managerid)
   (manager
    :accessor employee-manager
    :db-kind :join
    :db-info (:join-class employee
			  :home-key managerid
			  :foreign-key emplid
			  :set nil))
   (addresses
    :accessor employee-addresses
    :db-kind :join
    :db-info (:join-class employee-address
			  :home-key emplid
			  :foreign-key aemplid
			  :target-slot address
			  :set t)))
  (:base-table employee))

(def-view-class company ()
  ((companyid
    :db-kind :key
    :db-constraints :not-null
    :type integer
    :initarg :companyid)
   (groupid
    :db-kind :key
    :db-constraints :not-null
    :type integer
    :initarg :groupid)
   (name
    :type (varchar 100)
    :initarg :name)
   (presidentid
    :type integer
    :initarg :presidentid)
   (president
    :reader president
    :db-kind :join
    :db-info (:join-class employee
			  :home-key presidentid
			  :foreign-key emplid
			  :set nil))
   (employees
    :reader company-employees
    :db-kind :join
    :db-info (:join-class employee
			  :home-key (companyid groupid)
			  :foreign-key (ecompanyid groupid)
			  :set t))))

(def-view-class address ()
  ((addressid
    :db-kind :key
    :db-constraints :not-null
    :type integer
    :initarg :addressid)
   (street-number
    :type integer
    :initarg :street-number)
   (street-name
    :type (varchar 30)
    :void-value ""
    :initarg :street-name)
   (city
    :column "city_field"
    :void-value "no city"
    :type (varchar 30)
    :initarg :city)
   (postal-code
    :column zip
    :type integer
    :void-value 0
    :initarg :postal-code))
  (:base-table addr))

;; many employees can reside at many addressess
(def-view-class employee-address ()
  ((aemplid :type integer :initarg :emplid)
   (aaddressid :type integer :initarg :addressid)
   (verified :type boolean :initarg :verified)
   (address :db-kind :join
	    :db-info (:join-class address
				  :home-key aaddressid
				  :foreign-key addressid
				  :retrieval :immediate)))
  (:base-table "ea_join"))

(def-view-class deferred-employee-address ()
  ((aemplid :type integer :initarg :emplid)
   (aaddressid :type integer :initarg :addressid)
   (verified :type boolean :initarg :verified)
   (address :db-kind :join
	    :db-info (:join-class address
				  :home-key aaddressid
				  :foreign-key addressid
				  :retrieval :deferred
				  :set nil)))
  (:base-table "ea_join"))
      </screen>
    </refsect1>
    <refsect1>
      <title>Side Effects</title>
      <para>Creates a new CLOS class.</para>
    </refsect1>
    <refsect1>
      <title>Affected by</title>
      <para>
	Nothing.
      </para>
    </refsect1>
    <refsect1>
      <title>Exceptional Situations</title>
      <para>
	None.
      </para>
    </refsect1>
    <refsect1>
      <title>See Also</title>
      <para>
	<simplelist>
	  <member><link linkend="create-view-from-class"><function>create-view-from-class</function></link></member>
	  <member><link linkend="standard-db-object"><parameter>standard-db-object</parameter></link></member>
	  <member><link linkend="drop-view-from-class"><function>drop-view-from-class</function></link></member>
	</simplelist>
      </para>
    </refsect1>
    <refsect1>
      <title>Notes</title>
      <para>
	The actual SQL type for a column depends up the database type
	in which the SQL table is stored. As an example, the view
	class type <parameter>(varchar 100)</parameter> specifies a
	SQL column type <parameter>VARCHAR(100)</parameter> in &mysql;
	and a column type <parameter>VARCHAR2(100)</parameter> in
	&oracle;
      </para>
      <para>
	The actual lisp type for a slot may be different than the
	value specified by the <parameter>:type</parameter> attribute.
	For example, a slot declared with "<parameter>:type (string
	30)</parameter>" actually sets the slots Lisp type as
	<parameter>(or null string)</parameter>. This is to allow a
	&nil; value or a string shorter than 30 characters to be
	stored in the slot.
      </para>
    </refsect1>
  </refentry>

  <refentry id="drop-view-from-class">
    <refnamediv>
      <refname>DROP-VIEW-FROM-CLASS</refname>
      <refpurpose>Delete table from SQL database.</refpurpose>
      <refclass>Function</refclass>
    </refnamediv>
    <refsect1>
      <title>Syntax</title>
      <synopsis>
      <function>drop-view-from-class</function> <replaceable>view-class-name</replaceable> &amp;key <replaceable>database</replaceable> => <returnvalue><!-- result --></returnvalue></synopsis>
    </refsect1>
    <refsect1>
      <title>Arguments and Values</title>
      <variablelist>
	<varlistentry>
	  <term><parameter>view-class-name</parameter></term>
	  <listitem>
	    <para>
	      The name of the <glossterm linkend="gloss-view-class">View
	      Class</glossterm>.
	    </para>
	  </listitem>
	</varlistentry>
        <varlistentry>
          <term><parameter>database</parameter></term>
          <listitem>
            <para>
              <glossterm linkend="gloss-database-object">database
              object</glossterm>. This will default to the value of
              <symbol>*default-database*</symbol>.
	    </para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </refsect1>
    <refsect1>
      <title>Description</title>
      <para>Removes a table defined by the <glossterm
      linkend="gloss-view-class">View Class</glossterm>
      <parameter>view-class-name</parameter> from
      <parameter>database</parameter> which defaults to
      <parameter>*default-database*</parameter>.
      </para>
    </refsect1>
    <refsect1>
      <title>Examples</title>
      <screen>
(list-tables)
=> ("FOO" "BAR")
(drop-view-from-class 'foo)
=>
(list-tables)
=> ("BAR")
      </screen>
    </refsect1>
    <refsect1>
      <title>Side Effects</title>
      <para>
	Deletes a table from the SQL database.
      </para>
    </refsect1>
    <refsect1>
      <title>Affected by</title>
      <para>
	Whether the specified table exists in the SQL database.
      </para>
    </refsect1>
    <refsect1>
      <title>Exceptional Situations</title>
      <para>
	A condition may be signalled if the table does not exist in
	the SQL database or if the SQL connection does not have
	sufficient permissions to delete tables.
      </para>
    </refsect1>
    <refsect1>
      <title>See Also</title>
      <para>
	<simplelist>
	  <member><link linkend="create-view-from-class"><function>create-view-from-class</function></link></member>
	  <member><link linkend="def-view-class"><function>def-view-class</function></link></member>
	</simplelist>
      </para>
    </refsect1>
    <refsect1>
      <title>Notes</title>
      <para>
        None.
      </para>
    </refsect1>
  </refentry>

  <refentry id="list-classes">
    <refnamediv>
      <refname>LIST-CLASSES</refname>
      <refpurpose>List classes for tables in SQL database.</refpurpose>
      <refclass>Function</refclass>
    </refnamediv>
    <refsect1>
      <title>Syntax</title>
      <synopsis>
      <function>list-classes</function> &amp;key <replaceable>test</replaceable> <replaceable>root-class</replaceable> <replaceable>database</replaceable> => <returnvalue>classes</returnvalue></synopsis>
    </refsect1>
    <refsect1>
      <title>Arguments and Values</title>
      <variablelist>
	<varlistentry>
	  <term><parameter>test</parameter></term>
	  <listitem>
	    <para>
	      a function used to filter the search. By default, <parameter>identity</parameter> is used which
	      will return all classes.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><parameter>root-class</parameter></term>
	  <listitem>
	    <para>
	      specifies the root class to the search. By default,
	      <parameter>standard-db-object</parameter> is used which
	      is the root for all view classes.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><parameter>database</parameter></term>
	  <listitem>
	    <para>
	      The <glossterm
	      linkend="gloss-database-object">database</glossterm> to
	      search for view classes. This will default to the value
	      of <symbol>*default-database*</symbol>.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><parameter>classes</parameter></term>
	  <listitem>
	    <para>
	      List of view classes.
	    </para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </refsect1>
    <refsect1>
      <title>Description</title>
      <para>Returns a list of all the View Classes which have been
      defined in the Lisp session and are connected to
      <parameter>database</parameter> and which descended from the
      class <parameter>root-class</parameter> and which satisfy the
      function <parameter>test</parameter>.
      </para>
    </refsect1>
    <refsect1>
      <title>Examples</title>
      <screen>
(list-classes)
=> (#&lt;clsql-sys::standard-db-class big> #&lt;clsql-sys::standard-db-class employee-address>
    #&lt;clsql-sys::standard-db-class address> #&lt;clsql-sys::standard-db-class company>
    #&lt;clsql-sys::standard-db-class employee>)

(list-classes :test #'(lambda (c) (> (length (symbol-name (class-name c))) 3)))
=> (#&lt;clsql-sys::standard-db-class employee-address> #&lt;clsql-sys::standard-db-class address>
    #&lt;clsql-sys::standard-db-class company> #&lt;clsql-sys::standard-db-class employee>)
      </screen>
    </refsect1>
    <refsect1>
      <title>Side Effects</title>
      <para>
	None.
      </para>
    </refsect1>
    <refsect1>
      <title>Affected by</title>
      <para>
	<simplelist>
	  <member>Which view classes have been defined in the Lisp
	  session.</member>
	</simplelist>
      </para>
    </refsect1>
    <refsect1>
      <title>Exceptional Situations</title>
      <para>
	None.
      </para>
    </refsect1>
    <refsect1>
      <title>See Also</title>
      <para>
	<simplelist>
	  <member><link linkend="def-view-class"><function>def-view-class</function></link></member>
	</simplelist>
      </para>
    </refsect1>
    <refsect1>
      <title>Notes</title>
      <para>
        None.
      </para>
    </refsect1>
  </refentry>


</reference>