如何獲取特定列中值為空的記錄？

Question

我在某些項目中使用了flourishlib 。

假設我有一個名為categories(id, name, parent_id) ，其中parent_id是categories表的foreign key 。

我正在使用fRecordSet::build()選擇記錄集。 我想選擇沒有父母的記錄。 在MySQL中，這將是

select * from categories where parent_id is null

但是，我想使用fRecordSet::build做到這一點。 在文檔或示例中，我都沒有看到執行此操作的可能性，也沒有在方法上看到執行此操作的可能性。 是否有可能像上面顯示的查詢中那樣運行fRecordSet::build過濾？

供您參考，我要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);
}

非常感謝你。

Answer 1

好吧，長話短說：

select null = null

結果是

null

所以null不為null 。

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

起作用，也就是說，它會產生所有沒有parent_id的記錄。

當然，我一直在嘗試這樣做，但是，我以錯誤的方式嘗試了它。

我有一個生成fRecordSet::build調用的方法，該調用不會為我所有頁面上的所有類用法實現同一件事。 我正在使用AJAX將參數發布到服務器。 對於where子句，我發布以下內容：

{"parent_id=": null}

並且$_POST["parent_id"]不為null ，它是空字符串。 哇。

因此，解決方案是告訴服務器端，如果它是空字符串，則將值設置為null ，這在我的情況下適用，因為parent_id是一個數字，但是我想知道如果相同的控件應該如何解決我的問題？用於對字符串值進行過濾，其中空字符串是有效值。 因此，我遇到的問題與問題中提出的問題不同，但該問題可能對像我這樣的陌生人很有用，他們真的認為我們可以將null值從客戶端發布到服務器端。