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MySQL Cookbook
book

MySQL Cookbook

by Paul DuBois
October 2002
Intermediate to advanced content levelIntermediate to advanced
1024 pages
27h 26m
English
O'Reilly Media, Inc.
Content preview from MySQL Cookbook

Calculating Intervals Between Times

Problem

You want to know the amount of time elapsed between two times.

Solution

Convert the times to seconds with TIME_TO_SEC( ) and take the difference. For a difference represented as a time, convert the result back the other way using SEC_TO_TIME( ).

Discussion

Calculating intervals between times is similar to adding times together, except that you compute a difference rather than a sum. For example, to calculate intervals in seconds between pairs of t1 and t2 values, convert the values in the time_val table to seconds using TIME_TO_SEC( ), then take the difference. To express the resulting difference as a TIME value, pass it to SEC_TO_TIME( ). The following query shows intervals both ways:

mysql> SELECT t1, t2,
    -> TIME_TO_SEC(t2) - TIME_TO_SEC(t1) AS 'interval in seconds',
    -> SEC_TO_TIME(TIME_TO_SEC(t2) - TIME_TO_SEC(t1)) AS 'interval as TIME'
    -> FROM time_val;
+----------+----------+---------------------+------------------+
| t1       | t2       | interval in seconds | interval as TIME |
+----------+----------+---------------------+------------------+
| 15:00:00 | 15:00:00 |                   0 | 00:00:00         |
| 05:01:30 | 02:30:20 |               -9070 | -02:31:10        |
| 12:30:20 | 17:30:45 |               18025 | 05:00:25         |
+----------+----------+---------------------+------------------+

Note that intervals may be negative, as is the case when t1 occurs later than t2.

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Publisher Resources

ISBN: 0596001452Catalog PageErrata