如何获得在特定列中以null作为值的记录？

Question

我在我的一些项目中使用flourishlib。

假设我有一个名为categories(id, name, parent_id)的表，其中parent_id是categories表的foreign key。

我使用fRecordSet::build()来选择记录集。我想选择那些没有父母的记录。在MySQL中，这将是

select * from categories where parent_id is null

但是，我想使用fRecordSet::build来完成这个任务。我没有在文档中看到这样做的可能性，也没有在示例中看到这样做的可能性。是否有可能像上面所示的查询那样运行fRecordSet::build筛选？

供您参考，我想使用的方法如下所示：

/**
 * Creates an fRecordSet by specifying the class to create plus the where conditions and order by rules
 * 
 * The where conditions array can contain `key => value` entries in any of
 * the following formats:
 * 
 * {{{
 * 'column='                    => VALUE,                       // column = VALUE
 * 'column!'                    => VALUE                        // column <> VALUE
 * 'column!='                   => VALUE                        // column <> VALUE
 * 'column<>'                   => VALUE                        // column <> VALUE
 * 'column~'                    => VALUE                        // column LIKE '%VALUE%'
 * 'column^~'                   => VALUE                        // column LIKE 'VALUE%'
 * 'column$~'                   => VALUE                        // column LIKE '%VALUE'
 * 'column!~'                   => VALUE                        // column NOT LIKE '%VALUE%'
 * 'column<'                    => VALUE                        // column < VALUE
 * 'column<='                   => VALUE                        // column <= VALUE
 * 'column>'                    => VALUE                        // column > VALUE
 * 'column>='                   => VALUE                        // column >= VALUE
 * 'column=:'                   => 'other_column'               // column = other_column
 * 'column!:'                   => 'other_column'               // column <> other_column
 * 'column!=:'                  => 'other_column'               // column <> other_column
 * 'column<>:'                  => 'other_column'               // column <> other_column
 * 'column<:'                   => 'other_column'               // column < other_column
 * 'column<=:'                  => 'other_column'               // column <= other_column
 * 'column>:'                   => 'other_column'               // column > other_column
 * 'column>=:'                  => 'other_column'               // column >= other_column
 * 'column='                    => array(VALUE, VALUE2, ... )   // column IN (VALUE, VALUE2, ... )
 * 'column!'                    => array(VALUE, VALUE2, ... )   // column NOT IN (VALUE, VALUE2, ... )
 * 'column!='                   => array(VALUE, VALUE2, ... )   // column NOT IN (VALUE, VALUE2, ... )
 * 'column<>'                   => array(VALUE, VALUE2, ... )   // column NOT IN (VALUE, VALUE2, ... )
 * 'column~'                    => array(VALUE, VALUE2, ... )   // (column LIKE '%VALUE%' OR column LIKE '%VALUE2%' OR column ... )
 * 'column^~'                   => array(VALUE, VALUE2, ... )   // (column LIKE 'VALUE%' OR column LIKE 'VALUE2%' OR column ... )
 * 'column$~'                   => array(VALUE, VALUE2, ... )   // (column LIKE '%VALUE' OR column LIKE '%VALUE2' OR column ... )
 * 'column&~'                   => array(VALUE, VALUE2, ... )   // (column LIKE '%VALUE%' AND column LIKE '%VALUE2%' AND column ... )
 * 'column!~'                   => array(VALUE, VALUE2, ... )   // (column NOT LIKE '%VALUE%' AND column NOT LIKE '%VALUE2%' AND column ... )
 * 'column!|column2<|column3='  => array(VALUE, VALUE2, VALUE3) // (column <> '%VALUE%' OR column2 < '%VALUE2%' OR column3 = '%VALUE3%')
 * 'column|column2><'           => array(VALUE, VALUE2)         // WHEN VALUE === NULL: ((column2 IS NULL AND column = VALUE) OR (column2 IS NOT NULL AND column <= VALUE AND column2 >= VALUE))
 *                                                              // WHEN VALUE !== NULL: ((column <= VALUE AND column2 >= VALUE) OR (column >= VALUE AND column <= VALUE2))
 * 'column|column2|column3~'    => VALUE                        // (column LIKE '%VALUE%' OR column2 LIKE '%VALUE%' OR column3 LIKE '%VALUE%')
 * 'column|column2|column3~'    => array(VALUE, VALUE2, ... )   // ((column LIKE '%VALUE%' OR column2 LIKE '%VALUE%' OR column3 LIKE '%VALUE%') AND (column LIKE '%VALUE2%' OR column2 LIKE '%VALUE2%' OR column3 LIKE '%VALUE2%') AND ... )
 * }}}
 * 
 * When creating a condition in the form `column|column2|column3~`, if the
 * value for the condition is a single string that contains spaces, the
 * string will be parsed for search terms. The search term parsing will
 * handle quoted phrases and normal words and will strip punctuation and
 * stop words (such as "the" and "a").
 * 
 * The order bys array can contain `key => value` entries in any of the
 * following formats:
 * 
 * {{{
 * 'column'     => 'asc'      // 'first_name' => 'asc'
 * 'column'     => 'desc'     // 'last_name'  => 'desc'
 * 'expression' => 'asc'      // "CASE first_name WHEN 'smith' THEN 1 ELSE 2 END" => 'asc'
 * 'expression' => 'desc'     // "CASE first_name WHEN 'smith' THEN 1 ELSE 2 END" => 'desc'
 * }}}
 * 
 * The column in both the where conditions and order bys can be in any of
 * the formats:
 * 
 * {{{
 * 'column'                                                         // e.g. 'first_name'
 * 'current_table.column'                                           // e.g. 'users.first_name'
 * 'related_table.column'                                           // e.g. 'user_groups.name'
 * 'related_table{route}.column'                                    // e.g. 'user_groups{user_group_id}.name'
 * 'related_table=>once_removed_related_table.column'               // e.g. 'user_groups=>permissions.level'
 * 'related_table{route}=>once_removed_related_table.column'        // e.g. 'user_groups{user_group_id}=>permissions.level'
 * 'related_table=>once_removed_related_table{route}.column'        // e.g. 'user_groups=>permissions{read}.level'
 * 'related_table{route}=>once_removed_related_table{route}.column' // e.g. 'user_groups{user_group_id}=>permissions{read}.level'
 * 'column||other_column'                                           // e.g. 'first_name||last_name' - this concatenates the column values
 * }}}
 * 
 * In addition to using plain column names for where conditions, it is also
 * possible to pass an aggregate function wrapped around a column in place
 * of a column name, but only for certain comparison types. //Note that for
 * column comparisons, the function may be placed on either column or both.//
 * 
 * {{{
 * 'function(column)='   => VALUE,                       // function(column) = VALUE
 * 'function(column)!'   => VALUE                        // function(column) <> VALUE
 * 'function(column)!=   => VALUE                        // function(column) <> VALUE
 * 'function(column)<>'  => VALUE                        // function(column) <> VALUE
 * 'function(column)~'   => VALUE                        // function(column) LIKE '%VALUE%'
 * 'function(column)^~'  => VALUE                        // function(column) LIKE 'VALUE%'
 * 'function(column)$~'  => VALUE                        // function(column) LIKE '%VALUE'
 * 'function(column)!~'  => VALUE                        // function(column) NOT LIKE '%VALUE%'
 * 'function(column)<'   => VALUE                        // function(column) < VALUE
 * 'function(column)<='  => VALUE                        // function(column) <= VALUE
 * 'function(column)>'   => VALUE                        // function(column) > VALUE
 * 'function(column)>='  => VALUE                        // function(column) >= VALUE
 * 'function(column)=:'  => 'other_column'               // function(column) = other_column
 * 'function(column)!:'  => 'other_column'               // function(column) <> other_column
 * 'function(column)!=:' => 'other_column'               // function(column) <> other_column
 * 'function(column)<>:' => 'other_column'               // function(column) <> other_column
 * 'function(column)<:'  => 'other_column'               // function(column) < other_column
 * 'function(column)<=:' => 'other_column'               // function(column) <= other_column
 * 'function(column)>:'  => 'other_column'               // function(column) > other_column
 * 'function(column)>=:' => 'other_column'               // function(column) >= other_column
 * 'function(column)='   => array(VALUE, VALUE2, ... )   // function(column) IN (VALUE, VALUE2, ... )
 * 'function(column)!'   => array(VALUE, VALUE2, ... )   // function(column) NOT IN (VALUE, VALUE2, ... )
 * 'function(column)!='  => array(VALUE, VALUE2, ... )   // function(column) NOT IN (VALUE, VALUE2, ... )
 * 'function(column)<>'  => array(VALUE, VALUE2, ... )   // function(column) NOT IN (VALUE, VALUE2, ... )
 * }}}
 * 
 * The aggregate functions `AVG()`, `COUNT()`, `MAX()`, `MIN()` and
 * `SUM()` are supported across all database types.
 * 
 * Below is an example of using where conditions and order bys. Please note
 * that values should **not** be escaped for the database, but should just
 * be normal PHP values.
 * 
 * {{{
 * #!php
 * return fRecordSet::build(
 *     'User',
 *     array(
 *         'first_name='      => 'John',
 *         'status!'          => 'Inactive',
 *         'groups.group_id=' => 2
 *     ),
 *     array(
 *         'last_name'   => 'asc',
 *         'date_joined' => 'desc'
 *     )
 * );
 * }}}
 * 
 * @param  string  $class             The class to create the fRecordSet of
 * @param  array   $where_conditions  The `column => value` comparisons for the `WHERE` clause
 * @param  array   $order_bys         The `column => direction` values to use for the `ORDER BY` clause
 * @param  integer $limit             The number of records to fetch
 * @param  integer $page              The page offset to use when limiting records
 * @return fRecordSet  A set of fActiveRecord objects
 */
static public function build($class, $where_conditions=array(), $order_bys=array(), $limit=NULL, $page=NULL)
{
    fActiveRecord::validateClass($class);
    fActiveRecord::forceConfigure($class);

    $db     = fORMDatabase::retrieve($class, 'read');
    $schema = fORMSchema::retrieve($class);
    $table  = fORM::tablize($class);

    $params = array($db->escape("SELECT %r.* FROM :from_clause", $table));

    if ($where_conditions) {
        $having_conditions = fORMDatabase::splitHavingConditions($where_conditions);
    } else {
        $having_conditions = NULL;  
    }

    if ($where_conditions) {
        $params[0] .= ' WHERE ';
        $params = fORMDatabase::addWhereClause($db, $schema, $params, $table, $where_conditions);
    }

    $params[0] .= ' :group_by_clause ';

    if ($having_conditions) {
        $params[0] .= ' HAVING ';
        $params = fORMDatabase::addHavingClause($db, $schema, $params, $table, $having_conditions); 
    }

    // If no ordering is specified, order by the primary key
    if (!$order_bys) {
        $order_bys = array();
        foreach ($schema->getKeys($table, 'primary') as $pk_column) {
            $order_bys[$table . '.' . $pk_column] = 'ASC';  
        }
    }

    $params[0] .= ' ORDER BY ';
    $params = fORMDatabase::addOrderByClause($db, $schema, $params, $table, $order_bys);

    $params = fORMDatabase::injectFromAndGroupByClauses($db, $schema, $params, $table);

    // Add the limit clause and create a query to get the non-limited total
    $non_limited_count_sql = NULL;
    if ($limit !== NULL) {
        $pk_columns = array();
        foreach ($schema->getKeys($table, 'primary') as $pk_column) {
            $pk_columns[] = $table . '.' . $pk_column;  
        }

        $non_limited_count_sql = str_replace(
            $db->escape('SELECT %r.*', $table),
            $db->escape('SELECT %r', $pk_columns),
            $params[0]
        );
        $non_limited_count_sql = preg_replace('#\s+ORDER BY.*$#', '', $non_limited_count_sql);
        $non_limited_count_sql = $db->escape('SELECT count(*) FROM (' . $non_limited_count_sql . ') subquery', array_slice($params, 1));

        $params[0] .= ' LIMIT ' . $limit;

        if ($page !== NULL) {

            if (!is_numeric($page) || $page < 1) {
                $page = 1;
            }

            $params[0] .= ' OFFSET ' . (($page-1) * $limit);
        }
    } else {
        $page = 1;
    }

    return new fRecordSet($class, call_user_func_array($db->translatedQuery, $params), $non_limited_count_sql, $limit, $page);
}

非常感谢。

Answer 1

好吧，长话短说：

select null = null

结果：

null

所以null不是null。

fRecordSet::build("Category", array("parent_id=" => null))

工作，也就是说，它产生所有没有parent_id的记录。

当然，我一直在尝试这样做，但是，我尝试了错误的方法。

我有一个方法，它生成fRecordSet::build调用，不对我所有页面上的所有类使用实现相同的东西。我使用AJAX将参数发布到服务器。关于where条款，我张贴如下：

{"parent_id=": null}

$_POST["parent_id"]不是null，它是空字符串。哇。

因此，解决方案是告诉服务器端，如果它是空字符串，则将值设置为null，这在我的情况下是可行的，因为parent_id是一个数字，但是我想知道如果在字符串值上使用相同的控件来过滤空字符串是一个有效值，我将如何解决我的问题。因此，我遇到了一个与问题中所述不同的问题，但这个问题可能对像我这样的陌生人有用，他们认为我们可以将null值从客户端发布到服务器端。