Converting Between Times and Seconds

5.11.1 Problem

You have a time value but you want a value in seconds, or vice versa.

5.11.2 Solution

TIME values are specialized representations of a simpler unitsecondsand you can convert back and forth from one to the other using TIME_TO_SEC( ) and SEC_TO_TIME( ).

5.11.3 Discussion

TIME_TO_SEC( ) converts a TIME value to the equivalent number of seconds, and SEC_TO_TIME( ) does the opposite. The following query demonstrates a simple conversion in both directions:

mysql> SELECT t1,
 -> TIME_TO_SEC(t1) AS 'TIME to seconds',
 -> SEC_TO_TIME(TIME_TO_SEC(t1)) AS 'TIME to seconds to TIME'
 -> FROM time_val;
+----------+-----------------+-------------------------+
| t1 | TIME to seconds | TIME to seconds to TIME |
+----------+-----------------+-------------------------+
| 15:00:00 | 54000 | 15:00:00 |
| 05:01:30 | 18090 | 05:01:30 |
| 12:30:20 | 45020 | 12:30:20 |
+----------+-----------------+-------------------------+

To express time values as minutes, hours, or days, perform the appropriate divisions:

mysql> SELECT t1,
 -> TIME_TO_SEC(t1) AS 'seconds',
 -> TIME_TO_SEC(t1)/60 AS 'minutes',
 -> TIME_TO_SEC(t1)/(60*60) AS 'hours',
 -> TIME_TO_SEC(t1)/(24*60*60) AS 'days'
 -> FROM time_val;
+----------+---------+---------+-------+------+
| t1 | seconds | minutes | hours | days |
+----------+---------+---------+-------+------+
| 15:00:00 | 54000 | 900.00 | 15.00 | 0.62 |
| 05:01:30 | 18090 | 301.50 | 5.03 | 0.21 |
| 12:30:20 | 45020 | 750.33 | 12.51 | 0.52 |
+----------+---------+---------+-------+------+

Use FLOOR( ) if you prefer integer values to floating-point values:

mysql> SELECT t1,
 -> TIME_TO_SEC(t1) AS 'seconds',
 -> FLOOR(TIME_TO_SEC(t1)/60) AS 'minutes',
 -> FLOOR(TIME_TO_SEC(t1)/(60*60)) AS 'hours',
 -> FLOOR(TIME_TO_SEC(t1)/(24*60*60)) AS 'days'
 -> FROM time_val;
+----------+---------+---------+-------+------+
| t1 | seconds | minutes | hours | days |
+----------+---------+---------+-------+------+
| 15:00:00 | 54000 | 900 | 15 | 0 |
| 05:01:30 | 18090 | 301 | 5 | 0 |
| 12:30:20 | 45020 | 750 | 12 | 0 |
+----------+---------+---------+-------+------+

If you pass TIME_TO_SEC( ) a date-and-time value, it extracts the time part and discards the date. This provides yet another means of extracting times from DATETIME and TIMESTAMP values (in addition to those already discussed earlier in the chapter):

mysql> SELECT dt,
 -> TIME_TO_SEC(dt) AS 'time part in seconds',
 -> SEC_TO_TIME(TIME_TO_SEC(dt)) AS 'time part as TIME'
 -> FROM datetime_val;
+---------------------+----------------------+-------------------+
| dt | time part in seconds | time part as TIME |
+---------------------+----------------------+-------------------+
| 1970-01-01 00:00:00 | 0 | 00:00:00 |
| 1987-03-05 12:30:15 | 45015 | 12:30:15 |
| 1999-12-31 09:00:00 | 32400 | 09:00:00 |
| 2000-06-04 15:45:30 | 56730 | 15:45:30 |
+---------------------+----------------------+-------------------+
mysql> SELECT ts,
 -> TIME_TO_SEC(ts) AS 'time part in seconds',
 -> SEC_TO_TIME(TIME_TO_SEC(ts)) AS 'time part as TIME'
 -> FROM timestamp_val;
+----------------+----------------------+-------------------+
| ts | time part in seconds | time part as TIME |
+----------------+----------------------+-------------------+
| 19700101000000 | 0 | 00:00:00 |
| 19870305123015 | 45015 | 12:30:15 |
| 19991231090000 | 32400 | 09:00:00 |
| 20000604154530 | 56730 | 15:45:30 |
+----------------+----------------------+-------------------+