SQL::QueryBuilder::OO – Object oriented SQL query builder

SYNOPSIS

use SQL::QueryBuilder::OO;

$sql = sqlQueryBase::select(qw(id title description), {name => 'author'})
    ->from('article')
    ->innerJoin('users', 'userId')
    ->leftJoin({'comments' => 'c'}, sqlCondition::EQ('userId', 'c.from'))
    ->where(sqlCondition::AND(
            sqlCondition::EQ('category')->bind($cat),
            sqlCondition::NE('hidden')->bind(1)))
    ->limit(10,20)
    ->groupBy('title')
    ->orderBy({'timestamp' => 'DESC'});

$dbh->do($sql, undef, $sql->gatherBoundArgs());

DESCRIPTION

This module provides for an object oriented way to create complex SQL queries while maintaining code readability. It supports conditions construction and bound query parameters. While the module is named SQL::QueryBuilder::OO, this name is actually not used when constructing queries. The three main packages to build queries are sqlQueryBase, sqlCondition and sqlQuery.

The project is actually a port of PHP classes to construct queries used in one of my proprietary projects (which may explain the excessive use of the scope resolution operator (::) in the module’s sytax).

BUILDING QUERIES

The package to provide builder interfaces is called sqlQueryBase and has these methods:

SELECT queries

select(COLUMNS…[, OPTIONS])

Creates a SELECT query object. Columns to select default to * if none are given. They are otherwise to be specified as a list of expressions that can be literal column names or HASH references with column aliases.

Column names are quoted where appropriate:

# Build SELECT * query
$all = sqlQueryBase::select();

# Build SELECT ... query
$sql = sqlQueryBase::select(
   # literal column names
      qw(id title),
   # column alias
      {'u.username' => 'author', timestamp => 'authored'},
   # SELECT specific options
      [qw(SQL_CACHE SQL_CALC_FOUND_ROWS)]);

The references returned from the above statements are blessed into an internal package. Those internal packages will not be documented here, since they may be subject to change. Their methods, however, are those of a valid SQL SELECT statement. When constructing queries you’ll have to maintain the order of SQL syntax. This means, that the following will be treated as an error by perl itself:

$sql = sqlQueryBase::select()
      ->from('table')
      ->limit(10)
      ->where(...);

# -> Can't locate object method "where" via package "sqlSelectAssemble" at ...

The correct order would have been:

$sql = sqlQueryBase::select()
      ->from('table')
      ->where(...)
      ->limit(10);

The following methods are available to construct the query further:

from(TABLES…)

This obviously represents the “FROM” part of a select query. It accepts a list of string literals as table names or table aliases:

$sql = sqlQueryBase::select()->from('posts', {'user' => 'u'});

leftJoin(TABLE, CONDITION)
innerJoin(TABLE, CONDITION)
rightJoin(TABLE, CONDITION)

These methods extend the “FROM” fragment with a left, inner or right table join. The table name can either be a string literal or a HASH reference for aliasing table names.

The condition should either be an sqlCondition object (see Creating conditions):

# SELECT * FROM `table_a` LEFT JOIN `table_b` ON(`column_a` = `column_b`)
$sql = sqlQueryBase::select()
      ->from('table_a')
      ->leftJoin('table_b', sqlCondition::EQ('column_a', 'column_b'));

…or a string literal of a common column name for the USING clause:

# SELECT * FROM `table_a` LEFT JOIN `table_b` USING(`id`)
$sql = sqlQueryBase::select()
      ->from('table_a')
      ->leftJoin('table_b', 'id');

where(CONDITION)

This represents the “WHERE” part of a SELECT query. It will accept one object of the sqlCondition package (see Creating conditions).

groupBy(COLUMNS…)

This represents the “GROUP BY” statement of a SELECT query.

having(CONDITION)

This represents the “HAVING” part of a SELECT query. It will accept one object of the sqlCondition package (see Creating conditions).

orderBy(COLUMNS…)

This represents the “ORDER BY” statement of a SELECT query. Columns are expected to be string literals or HASH references (one member only) with ordering directions:

$sql = sqlQueryBase::select()
      ->from('table')
      ->orderBy('id', {timestamp => 'DESC'}, 'title');

limit(COUNT[, OFFSET])

This represents the “LIMIT” fragment of a SELECT query. It deviates from the standard SQL expression, as the limit count is always the first argument to this method, regardless of a given offset.

=back

Creating conditions

Conditions can be used as a parameter for leftJoin, having, innerJoin, rightJoin or where. They are constructed with the sqlCondition package, whose methods are not exported due to their generic names. Instead, the “namespace” has to be mentioned for each conditional:

$cond = sqlCondition::AND(
      sqlCondition::EQ('id')->bind(1337),
      sqlCondition::BETWEEN('stamp', "2013-01-06", "2014-03-31"));

Those are all operators:

Booleans

To logically connect conditions, the following to methods are available:

AND(CONDITIONS…)

Connect one or more conditions with a boolean AND.

OR(CONDITIONS…)

Connect one or more conditions with a boolean OR.

NOT(CONDITION)

Negate a condition with an unary NOT.

Relational operators

All relational operators expect a mandatory column name as their first argument and a second optional ride-hand-side column name.

If the optional second parameter is left out, the conditional can be bound (see Binding parameters).

EQ(COLUMN, [RHS-COLUMN])

Equal to operator (=).

NE(COLUMN, [RHS-COLUMN])

Not equal to operator (!=).

LT(COLUMN, [RHS-COLUMN])

Less than operator (<).

GT(COLUMN, [RHS-COLUMN])

Greater than operator (>).

LTE(COLUMN, [RHS-COLUMN])

Less than or equal to operator (<=).

GTE(COLUMN, [RHS-COLUMN])

Greater than or equal to operator (>=).

SQL specific operators

BETWEEN(COLUMN, START, END)

Creates an “x BETWEEN start AND end” conditional.

IN(COLUMN)

Creates an “x IN(…)” conditional.

Note that, if bound, this method will croak if it encounters an empty list. This behavior is subject to change in future versions: the statement will be reduced to a “falsy” statement and a warning will be issued.

ISNULL(COLUMN)

Creates an “x IS NULL” conditional.

ISNOTNULL(COLUMN)

Creates an “x IS NOT NULL” conditional.

LIKE(COLUMN, PATTERN)

Creates an “x LIKE pattern” conditional.

Note that the pattern is passed unmodified. Beware of the LIKE pitfalls concerning the characters % and _.

Binding parameters

An SQL conditional can be bound against a parameter via its bind() method:

$cond = sqlCondition::AND(
      sqlCondition::EQ('id')->bind(1337),
      sqlCondition::NOT(
         sqlCondition::IN('category')->bind([1,2,3,4])));

print $cond;                        # "`id` = ? AND NOT(`category` IN(?))"
@args = $cond->gatherBoundArgs();   # (sqlValueInt(1337),sqlValueList([1,2,3,4]))

A special case are conditionals bound against undef (which is the equivalent to SQL NULL):

$cat = undef;
$cond = sqlCondition::OR(
      sqlCondition::EQ('author')->bind(undef),
      sqlCondition::NE('category')->bind($cat));

print $cond;                        # `author` IS NULL OR `category` IS NOT NULL
@args = $cond->gatherBoundArgs();   # ()

Since `author` = NULL would never be “true”, the condition is replaced with the correct `author` IS NULL statement.

(Note that the first conditional could actually be written sqlCondition::ISNULL('author'). The substitution is thus useful when binding against variables of unknown content).

TODO

Implement support for UPDATE, INSERT, REPLACE and DELETE statements.
Implement support for UNION.

DEPENDENCIES

Params::Validate

COPYRIGHT

This software is a free library. You can modify and/or distribute it under the same terms as Perl itself.

AUTHOR

Oliver Schieche <schiecheo@cpan.org>

http://perfect-co.de/

$Id: OO.pm 21 2014-03-31 11:46:37Z schieche $

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