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Author image Igor Plisco

NAME

DBIx::Composer - Composes and runs SQL statement.

SYNOPSIS

  use DBIx::Composer
  $cmd = new DBIx::Composer();
  $cmd->{table} = 'table1';
  $cmd->{fields} = 'name, email';
  $cmd->{where} = "where login = 'peter'";
  print $cmd->compose_select;
# Prints "select name, surname from table1 where login = 'peter'"

  $dbh = open_database();       # Open database yourself
  use DBIx::Composer
  $cmd = new DBIx::Composer(dbh=>$dbh, debug=> 1);
  $cmd->{table} = 'table1';
  $cmd->{fields} = 'login, name, email';
  $cmd->{values} = "'john', 'John Smith', 'john@smith.com'";
  $cmd->insert();
# Executes command "insert into table1 (login, name, email) values 
#    ('john', 'John Smith', 'john@smith.com')"
# Prints this command on STDERR before execution.

DESCRIPTION

This module helps you to compose and run SQL statements. First you create new object and fill its hash for common parts of SQL statements. Then you may either compose SQL statement from these parts or both compose and execute it.

USAGE

You connect to database using your favorite method of connection and supply DBIx::Composer object with standard database handler $dbh. If you don't plan to execute statements, you may omit connection to database.

So, after creating new object you set its parameters, or SQL command parts. Modifiers for command, such as "where ...", "order ...", "limit ..." must be full modifiers like "where a=b", not only "a=b".

You don't need to prepare() SQL fetch statements - they are prepared internally. You cant execute statements right after setting their parts - the module checks whether command has been composed, prepared and executed. Because of such behaviour don't try to reset command parts after executing, but better create new DBIx::Composer object.

Command parts

Valid command parts are:

  table - table name.
  Examples:
  $cmd->{table} = 'table1'
  $cmd->{table} = 'db left join user using (host)';

  fields - fields to select, insert, update, etc.
  Examples:
  $cmd->{fields} = 'login, email, tries + 5';
  $cmd->{fields} = 'curdate(), now()';
  $cmd->{fields} = 'ip, traf_in+thaf_out as sum';

  where
  Examples:
  $cmd->{where} = 'login = peter';
  $cmd->{where} = 'tries > limit + 2';

  order
  Examples:
  $cmd->{order} = "order by ip desc";

  limit
  Examples:
  $cmd->{limit} = "limit 20";
  $cmd->{limit} = "limit 100, 20";

Opening database

DBIx::Composer doesn't touch opening database. You should open it yourself somewhere else in your program. As for me, I use special function open_database() like this:

  #====================
  sub open_database {
  #====================
  
  # Read config from some file
    my ($db_db, $db_login, $db_passwd, $debug) = read_config();
    $driver_name = "dbi:mysql:$db_db";
    
  # Connect to database
    $dbh = DBI->connect
      ($driver_name, $db_login, $db_passwd)||
      die $DBI::errstr;
        
  # Initialize DBIx::Composer
    $DBIx::Composer::DBH = $dbh;
    $DBIx::Composer::DEBUG = $debug;

    return $dbh;        # returns true on success
  }

Then in your program you don't need to set $dbh anymore, so you can simply write:

  $cmd = new $DBIx::Composer;

and $cmd knows yet about dbh handler and debug level.

You have to set $dbh in new() explicitly only if you want to make two or more database connections in one program, e.g. on migrating from old database to new one.

Debug levels

If debug level is set to 1 or more, the module prints SQL commands to STDERR (for cgi scripts it's error_log of web server).

If debug level >= 1, it prints executed statements before executing them.

If debug level >= 2, it prints composed statements after composing them. So usually (not always) on level 2 you have 2 lines in STDERR - of composing and of executing.

Debug line starts from prefix ("SQL run" or "SQL debug") and program name (it's convenient for cgi-bin's).

Things you must pay attention to

  • In order to avoid confusing, don't reuse DBIx::Composer objects after executing them, but simply create new object. It's because the module remembers its state and don't composes statement again. Probably such behaviour will change partially in future.

  • Command parts 'where', 'limit', 'order' must be started from these words, that is, 'where a=b', not 'a=b'; 'order by c desc', not 'c desc' or 'by c desc'. You may have in your mind the string "select $fields from $table $where".

REQUIRES

  Perl 5.6.1 (for lvalue functions)
  ExtUtils::MakeMaker   - for installation
  Test::More    - for installation tests
  DBI etc.      - if you want to execute statements

BUGS

I have tested it only in environment with MySQL database and localhost as database host.

Installation tests doesn't check that it works on real database - they only check that the module composes statements.

AUTHOR

        Igor Plisco
        igor at plisco dot ru
        http://plisco.ru/soft

COPYRIGHT

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.

SEE ALSO

perl(1).

FUNCTION DESCRIPTIONS

new

 Purpose   : Creates new DBIx::Object object.
 Usage     : DBIx::Composer->new()
 Returns   : Object handler.
 Argument  : Nothing or dbh handler or config.
 Throws    : None.
 Comments  : No.

See Also : N/A

debug_level

 Usage     : DBIx::Composer->debug_level()
 Purpose   : Sets default debug level for all newly created objects.
 Returns   : current value of debug level
 Argument  : Debug level as integer.
 Throws    : None.
 Comments  : Warning: now returns global $dbh, not local for object.

See Also :

dbh

 Usage     : DBIx::Composer->dbh()
 Purpose   : Sets default database handler for all newly created objects.
 Returns   : current value of $dbh
 Argument  : database handler
 Throws    : None.
 Comments  : Warning: now returns global $dbh, not local for object.

See Also :

quote

 Usage     : DBIx::Composer->quote()
 Purpose   : Quotes its value by calling $dbh->quote.
 Returns   : Quoted string
 Argument  : String or number to quote
 Throws    : None.
 Comments  : None.

See Also :

compose_select

 Usage     : $cmd->compose_select()
 Purpose   : Composes select statement for given object.
 Returns   : Composed statement
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : Composes "select $fields from $table $where $order $limit"
  statement where $fields stands for $cmd->fields and so on.
  $where, $group, $order and $limit are optional.

See Also :

compose_insert

 Usage     : $cmd->compose_insert()
 Purpose   : Composes insert statement for given object.
 Returns   : Composed statement
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : Composes "insert into $table ($fields) values ($values)"
  or "insert into $table values ($values)" if $fields omitted.

See Also :

compose_replace

 Usage     : $cmd->compose_replace()
 Purpose   : Composes replace statement for given object.
 Returns   : Composed statement
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : Composes "replace into $table ($fields) values ($values)"
  or "replace into $table values ($values)" if $fields omitted.

See Also :

compose_delete

 Usage     : $cmd->compose_delete()
 Purpose   : Composes delete statement for given object.
 Returns   : Composed statement
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : Composes "delete from $table $where"
  or "delete from $table" if $where omitted.

See Also :

compose_update

 Usage     : $cmd->compose_update()
 Purpose   : Composes update statement for given object.
 Returns   : Composed statement
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : Composes "update $table $set $where"
  or "update $table $set" if $where omitted.

See Also :

selectrow_array

 Usage     : $cmd->selectrow_array()
 Purpose   : Makes DBI call of selectrow_array
 Returns   : Array or scalar
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : 

See Also :

fetch

 Usage     : $cmd->fetch()
 Purpose   : Makes DBI call of fetch
 Returns   : Array of data
 Argument  : None.
 Throws    : Returns undef, if error occured. See $dbh->errstr for errors. 
 Comments  : After last row returns undef too.

See Also :

fetchrow_hashref

 Usage     : $cmd->fetchrow_hashref()
 Purpose   : Makes DBI call of fetchrow_hashref
 Returns   : Array of data
 Argument  : None.
 Throws    : Returns undef, if error occured. See $dbh->errstr for errors. 
 Comments  : After last row returns undef too.

See Also :

insert

 Usage     : $cmd->insert()
 Purpose   : Makes DBI call of insert
 Returns   : ID of inserted row (as "last insert id").
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : 

See Also :

replace

 Usage     : $cmd->replace()
 Purpose   : Makes DBI call of replace
 Returns   : ID of replaced row (as "last insert id").
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : 

See Also :

delete

 Usage     : $cmd->delete()
 Purpose   : Makes DBI call of delete
 Returns   : 1 if OK, false otherwise.
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : 

See Also :

update

 Usage     : $cmd->update()
 Purpose   : Makes DBI call of update
 Returns   : 1 if OK, false otherwise.
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : 

See Also :

log_cmd

 Usage     : $cmd->log_cmd()
 Purpose   : Logs SQL command to STDERR.
 Returns   : Nothing.
 Argument  : 1 - output format
 Throws    : Returns undef, if required fields are missed.
 Comments  : Should't be called directly. Set flag debug
                instead when called new().

See Also :

debug

 Usage     : $cmd->debug()
 Purpose   : Logs SQL command to STDERR.
 Returns   : Nothing.
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : Should't be called directly. Set flag debug > 0
                instead when called new().

See Also :

log

 Usage     : $cmd->log()
 Purpose   : Logs SQL command to STDERR.
 Returns   : Nothing.
 Argument  : None.
 Throws    : Returns undef, if required fields are missed.
 Comments  : Should't be called directly. Set flag debug > 1
                instead when called new().

See Also :

Functions for access to inner object data as lvalue

 Usage     : $cmd->table = "users"; or: $table_sav = $cmd->table;
 Purpose   : Make access to inner variables without hash curlies.
 Comments  : Warning: don't work in Perl < 5.6. Use form $cmd->{table} instead.

 Currently supported functions:
        table()
        fields()
        values()
        where()
        set()
        order()
        group()
        limit()

2 POD Errors

The following errors were encountered while parsing the POD:

Around line 156:

'=item' outside of any '=over'

Around line 169:

You forgot a '=back' before '=head1'