How to get lowest value from table - mysql

Question

Problem 1
How can I get lowest value from table (not null), for ID_CAR? For example, for ID_CAR 1 lowest value is 50, for ID_CAR 2 lowest value is 50 and for ID_CAR 3 lowest value is 300. I don't need duplicates, I need only one value for one car.
ID_CAR | col_1 | col_2 | col_3 | col_4 | col_5 | col_6
1 | null | 250 | 300 | null | 900 | null
2 | 100 | null | 300 | 600 | 200 | 100
1 | 300 | 100 | 800 | 100 | 50 | 900
3 | 300 | 4000 | null | null | null | null
2 | null | null | null | 50 | null | 100
4 | 400 | 900 | 500 | 700 | 800 | 500
Problem 2
In this example, values in col_* are days. I need to add days to col_date and get lowest. For example lowest date for ID_CAR 1 is 2018-01-03 (col_2) and for ID_CAR 2 is 2018-01-15 (col_4).
ID_CAR | col_1 | col_2 | col_3 | col_4 | col_5 | col_6 | col_date
1 | null | 2 | 3 | null | 5 | null | 2018-01-01
2 | 1 | null | 3 | 6 | 10 | 10 | 2018-01-13
1 | 3 | 20 | 80 | 10 | 50 | 90 | 2018-01-02
3 | 30 | 40 | null | null | null | null | 2018-01-03
2 | null | null | null | 5 | null | 10 | 2018-01-10
4 | 10 | 9 | 5 | 70 | 8 | 50 | 2018-01-07

Answer 1

Without union you can simply combine least and min function :
select
ID_CAR,min(least(col_1,col_2,col_3,col_4,col_5,col_6)) lowest_value
from
table
group by
ID_CAR
or if you have nullvalues you need ifnull or coalesce function
select
ID_CAR,
min(least(
ifnull(col_1,~0),
ifnull(col_2,~0),
ifnull(col_3,~0),
ifnull(col_4,~0),
ifnull(col_5,~0),
ifnull(col_6,~0)
)) as lowest_value
from
table
group by
ID_CAR
~0 is the max bigint in mysql
The opposite function of least is greatest
The opposite function of min is max ;-)
Works with Mysql, Oracle, Postgres, Hive ...
Problem 2, something like this :
select
ID_CAR,
min(least(
DATE_ADD(col_date, INTERVAL ifnull(col_1,0) DAY),
DATE_ADD(col_date, INTERVAL ifnull(col_2,0) DAY),
DATE_ADD(col_date, INTERVAL ifnull(col_3,0) DAY),
DATE_ADD(col_date, INTERVAL ifnull(col_4,0) DAY),
DATE_ADD(col_date, INTERVAL ifnull(col_5,0) DAY),
DATE_ADD(col_date, INTERVAL ifnull(col_6,0) DAY)
)) as lowest_date
from
table
group by
ID_CAR
or like this (except if all columns can be null):
select
ID_CAR,
DATE_ADD(col_date, INTERVAL min(least(
ifnull(col_1,~0),
ifnull(col_2,~0),
ifnull(col_3,~0),
ifnull(col_4,~0),
ifnull(col_5,~0),
ifnull(col_6,~0)
)) DAY) as lowest_date
from
table
group by
ID_CAR

Answer 2

You need UNION :
select id_car, min(val) as lowest_value
from (select id_car, col_1 as Val
from table union
select id_car, col_2
from table
. . .
) t
group by id_car;

Answer 3

The following query will give you the required result
select tab.ID_CAR, min(tab.val) as lowest_value from
(
(select ID_CAR,min(col_1) val
from table
group by ID_CAR)
union
(select ID_CAR,min(col_2) val
from table
group by ID_CAR)
union
(select ID_CAR,min(col_3) val
from table
group by ID_CAR)
union
(select ID_CAR,min(col_4) val
from table
group by ID_CAR)
union
(select ID_CAR,min(col_5) val
from table
group by ID_CAR)
union
(select ID_CAR,min(col_6) val
from table
group by ID_CAR)
) tab
group by tab.ID_CAR

Answer 4

Try this
If you are expecting values greater than 9999999999999999999, then use a higher values
select id_car,
min(least(coalesce(col_1,9999999999999999999),coalesce(col_2,9999999999999999999),coalesce(col_3,9999999999999999999),
coalesce(col_4,9999999999999999999),coalesce(col_5,9999999999999999999),coalesce(col_6,9999999999999999999)
)
) as min_val
from your_table
group by id_car

Answer 5

The naive approach would be using least:
SELECT ID_CAR, least(t.col_1, t.col_2, t.col_3, t.col_4, t.col_5, t.col_6)
FROM
(SELECT ID_CAR, min(col_1) as col_1, min(col_2) as col_2, min(col_3) as col_3, min(col_4) as col_4, min(col_5) as col_5, min(col_6) as col_6
FROM YOUR_TABLE GROUP BY ID_CAR) t;
However: If ANY argument to LEAST is NULL, it'll return NULL. You'll either need to convert the NULLs to a high value (which is a hack but will work in practice, see other answers for this).
Which means doing something like this:
SELECT ID_CAR, LEAST(col_1, col_2, col_3,
col_4, col_5, col_6) as l
FROM
(SELECT ID_CAR,
IFNULL(min(col_1), 9999) as col_1,
IFNULL(min(col_2), 9999) as col_2,
IFNULL(min(col_3), 9999) as col_3,
IFNULL(min(col_4), 9999) as col_4,
IFNULL(min(col_5), 9999) as col_5,
IFNULL(min(col_6), 9999) as col_6
FROM YOUR_TABLE GROUP BY ID_CAR) t;
However, it might be good to use a trick to convert your table
into a three row table of the form:
car_id | attr | value
1 1 NULL ; or use strings such as "size"
1 2 250