Doctrine\DBAL\Platforms\DB2Platform::getAlterColumnClausesSQL PHP Method

    private function getAlterColumnClausesSQL(ColumnDiff $columnDiff)
    {
        $column = $columnDiff->column->toArray();
        $alterClause = 'ALTER COLUMN ' . $columnDiff->column->getQuotedName($this);
        if ($column['columnDefinition']) {
            return array($alterClause . ' ' . $column['columnDefinition']);
        }
        $clauses = array();
        if ($columnDiff->hasChanged('type') || $columnDiff->hasChanged('length') || $columnDiff->hasChanged('precision') || $columnDiff->hasChanged('scale') || $columnDiff->hasChanged('fixed')) {
            $clauses[] = $alterClause . ' SET DATA TYPE ' . $column['type']->getSQLDeclaration($column, $this);
        }
        if ($columnDiff->hasChanged('notnull')) {
            $clauses[] = $column['notnull'] ? $alterClause . ' SET NOT NULL' : $alterClause . ' DROP NOT NULL';
        }
        if ($columnDiff->hasChanged('default')) {
            if (isset($column['default'])) {
                $defaultClause = $this->getDefaultValueDeclarationSQL($column);
                if ($defaultClause) {
                    $clauses[] = $alterClause . ' SET' . $defaultClause;
                }
            } else {
                $clauses[] = $alterClause . ' DROP DEFAULT';
            }
        }
        return $clauses;
    }