MySQL - Using a date range vs functions

SELECT *
FROM tbl_preco
WHERE isActive = 1 
AND start_date < '2014-12-13 11:45:00' 
AND end_date > '2014-12-11 15:45:00';

select t.*
from t
where find_in_set(date_format(curdate(), '%Y-%m-%d'), datecol) > 0 or
      (datecol like '%,%' and datecol not like '%,%,%' and
       date_format(curdate(), '%Y-%m-%d') between substring_index(datecol, ',', 1) and substring_index(datecol, ',', -1)
      );

          ->whereNotBetween('excluded_period_start', [$start, $end])
          ->whereNotBetween('excluded_period_end', [$start, $end])

$quu ="SELECT
tableCalculated.lenght,
tableCalculated.timeACalculated AS timeA,
tableCalculated.timeBCalculated AS timeB,
TIMEDIFF(tableCalculated.timeBCalculated, tableCalculated.timeACalculated) AS period
FROM 
(
SELECT
lenght,
timeA,
(CASE 
    WHEN TIMEDIFF(timeA, '$zistart') < 0 THEN '$zistart' 
    WHEN TIMEDIFF(timeA, '$zistart') > 0 THEN timeA END) AS timeACalculated,
timeB,
(CASE 
    WHEN TIMEDIFF(timeB,'$ziend') < 0 THEN timeB
    WHEN TIMEDIFF(timeB,'$ziend') > 0 THEN '$ziend' END) AS timeBCalculated
FROM
`apm_travel_sheet` 
WHERE 
imei = '$imei' 
HAVING 
timeBCalculated <= '$ziend' AND timeACalculated >= '$zistart' ORDER BY id ASC
) AS tableCalculated  
HAVING period > 0";