How to get records having null as value in specific columns?

Question

I am using flourishlib in some of my projects.

Let's suppose that I have a table called categories(id, name, parent_id), where parent_id is a foreign key to the categories table.

I am using fRecordSet::build() to select record sets. I would like to select the records which do not have a parent. In MySQL this would be

select * from categories where parent_id is null

however, I would like to do this using fRecordSet::build. I have not seen possibilities to do this in the documentation, nor examples, also, I did not see the possibility to do this looking at the method. Is there a possibility to run fRecordSet::build filtering like in the query shown above?

For your reference, the method I would like to use looks like this:

/**
 * 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);
}

Thank you very much.

Answer 1

Ok, long story short:

select null = null

results in

null

So null is not null.

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

works, that is, it yields all the records which do not have a parent_id.

Of course, I have been trying to do this, however, I have tried it in the wrong way.

I have a method which generates the fRecordSet::build calls to not implement the same thing for all the class usages on all my pages. I am using AJAX to post the parameters to the server. For the where clause I post this:

{"parent_id=": null}

and $_POST["parent_id"] is not null, it is empty string. Wow.

So, the solution was to tell the server-side to set the value to null if it was empty string, which works in my case, as the parent_id is a number, but I wonder how will I solve my problem if the same controls should be used on string values for filtering where empty string is a valid value. So I had a different problem than stated in the question, but the question might be useful for strange people like myself who really think that we can post null values from client-side to server-side.