DBIx::Custom::Where

简介

DBIx::Custom::Where模块用于生成where子句。

# Create DBIx::Custom::Where object
my $where = $dbi->where;

# Clause
$where->clause(['and', 'title like :title', 'price = :price']);
$where->clause(['and', ':title{like}', ':price{=}']);

# Stringify where clause
my $where_clause = "$where";
my $where_clause = $where->to_string;
  # -> where title like :title and price = :price

# Only price condition
$where->clause(['and', ':title{like}', ':price{=}']);
$where->param({price => 1900});
  # -> where price = :price

# Only title condition
$where->clause(['and', ':title{like}', ':price{=}']);
$where->param({title => 'Perl'});
  # -> where title like :title

# Nothing
$where->clause(['and', ':title{like}', ':price{=}']);
$where->param({});
  # => Nothing

# or condition
$where->clause(['or', ':title{like}', ':price{=}']);
  # -> where title = :title or price like :price

# More than one parameter
$where->clause(['and', ':price{>}', ':price{<}']);
$where->param({price => [1000, 2000]});
  # -> where price > :price and price < :price

# Only first condition
$where->clause(['and', ':price{>}', ':price{<}']);
$where->param({price => [1000, $dbi->not_exists]});
  # -> where price > :price

# Only second condition
$where->clause(['and', ':price{>}', ':price{<}']);
$where->param({price => [$dbi->not_exists, 2000]});
  # -> where price < :price

# More complex condition
$where->clause(
  [
    'and',
    ':price{=}',
    ['or', ':title{=}', ':title{=}', ':title{=}']
  ]
);
  # -> pirce = :price and (title = :title or title = :title or tilte = :title)

# Using Full-qualified column name
$where->clause(['and', ':book.title{like}', ':book.price{=}']);
  # -> book.title like :book.title and book.price = :book.price

属性

clause

my $clause = $where->clause;
$where = $where->clause(
  ['and',
    ':title{=}', 
    ['or', ':date{<}', ':date{>}']
  ]
);

一个数组引用，存储where子中的所有where项，用于在调用to_string方法时生成where子句。

where title = :title and ( date < :date or date > :date )

param

my $param = $where->param;
$where = $where->param({
  title => 'Perl',
  date => ['2010-11-11', '2011-03-05'],
});

用于生成where子句的参数。

dbi

my $dbi = $where->dbi;
$where = $where->dbi($dbi);

DBIx::Custom对象。

join

my $join = $where->join;
$join = $where->join($join);

边连接的信息，这个值会被添加到select方法的join选项中。

方法

DBIx::Custom::Where继承了Object::Simple中的所有方法，并且实现了一个to_string方法。

$where->to_string;

用于将当前DBIx::Custom::Where对象转化为where子句。

重载的操作符

use overload
  'bool'   => sub {1},
  '""'     => sub { shift->to_string },
  fallback => 1;

clause 语法

clause 必须是一个以and 或 or 字符串为首元素的数组引用，里面的元素可以是字符串（后面称其为where项），也可以一个clause。也就是说clause是可以嵌套的。

而对于clause中的where项的格式可以有以下几种：

1. 没有占位符的一个条件式（ x=y）
2. 带有占位符的条件式（x= :y）
3. 自带操作符的占位符（:x{>}），可用的操作符有：like，>，<，=。

需要注意的是：当对DBIx::Custom::Where对象指定param属性时，在clause中存在而在parame中不存在的项，再调用to_string生成where子句时会被忽略。

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