CODEWITHSUNDEEP
mysqlcount
RonEskinder
RonEskinder

Reputation: 527

Repeated and grouped values in Mysql

How to calculate how many times the value 0 is repeated in a table only if that value is constant by 3 or more times (constant being repeated in next row)

in this case it would be 2 occasions that the value 0 is repeated more than 3 times.

+-----------+-------+---------------------+
| idDataGps | speed | eventDate           |
+-----------+-------+---------------------+
|    143483 |    56 | 2017-05-18 08:42:05 |
|    143484 |     0 | 2017-05-18 08:42:11 |
|    143485 |     0 | 2017-05-18 08:42:20 |
|    143486 |     0 | 2017-05-18 08:42:35 |
|    143487 |    43 | 2017-05-18 08:42:40 |
|    143488 |    44 | 2017-05-18 08:42:50 |
|    143489 |    48 | 2017-05-18 08:43:05 |
|    143490 |    24 | 2017-05-18 08:43:14 |
|    143491 |    34 | 2017-05-18 08:43:16 |
|    143492 |     9 | 2017-05-18 08:43:20 |
|    143493 |    14 | 2017-05-18 08:43:36 |
|    143494 |     0 | 2017-05-18 08:44:06 |
|    143495 |     0 | 2017-05-18 08:44:21 |
|    143496 |     0 | 2017-05-18 08:46:06 |
|    143497 |     0 | 2017-05-18 08:48:36 |
|    143498 |     0 | 2017-05-18 08:48:42 |
+-----------+-------+---------------------+

Upvotes: 0

Views: 81

Answers (1)

Barmar
Barmar

Reputation: 781350

Use user-defined variables to keep state from one row to the next. Use one variable @zerocount to count consecutive zero speeds; it gets reset back to 0 whenever speed != 0, and increments whenever speed = 0. Another variable @counter gets incremented whenever a non-zero value is encountered, so all the consecutive zeroes will be in the same @counter group.

Then to find out how long the run of zeroes is, we use MAX(zerocount) grouped by counter.

SELECT COUNT(*) FROM (
    SELECT counter, MAX(zerocount) AS maxcount
    FROM (
        SELECT speed, IF(speed = 0, @zerocount := @zerocount+1, @zerocount := 0) as zerocount,
            IF(speed != 0, @counter := @counter + 1, @counter) AS counter
        FROM (SELECT speed FROM yourTable ORDER BY eventDate) AS t
        CROSS JOIN (SELECT @counter := 0, @zerocount := 0) AS var
    ) AS x
    GROUP BY counter
) AS y
WHERE maxcount >= 3

DEMO

Upvotes: 1

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