자답이네요... 찾았습니다.^^
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switch($operation) {
                case 'equal' :
                        return $name.' = '.$value;
                    break;
                case 'more' :
                        return $name.' >= '.$value;
                    break;
                case 'excess' :
                        return $name.' > '.$value;
                    break;
                case 'less' :
                        return $name.' <= '.$value;
                    break;
                case 'below' :
                        return $name.' < '.$value;
                    break;
                case 'like_tail' :
                case 'like_prefix' :
                case 'like' :
                        return $name.' like '.$value;
                    break;
                case 'in' :
                        return $name.' in ('.$value.')';
                    break;
                case 'notin' :
                        return $name.' not in ('.$value.')';
                    break;
                case 'notequal' :
                        return $name.' <> '.$value;
                    break;
                case 'notnull' :
                        return $name.' is not null';
                    break;
                case 'null' :
                        return $name.' is null';
                    break;
            }