How do I find the maximum (or minimum) of two integers in Postgres/SQL? One of the integers is not a column value.
I will give an example scenario:
I would like to subtract an integer from a column (in all rows), but the result should not be less than zero. So, to begin with, I have:
UPDATE my_table
SET my_column = my_column - 10;
But this can make some of the values negative. What I would like (in pseudo code) is:
UPDATE my_table
SET my_column = MAXIMUM(my_column - 10, 0);
Have a look at GREATEST and LEAST.
UPDATE my_table
SET my_column = GREATEST(my_column - 10, 0);
You want the inline sql case:
set my_column = case when my_column - 10 > 0 then my_column - 10 else 0 end
max() is an aggregate function and gets the maximum of a row of a result set.
Edit: oops, didn't know about greatest and least in postgres. Use that instead.
Related
I have this sample database:
Table 1:
Type Condition_weight Price
A >50 1000
A >10 & <50 500
A <10 100
As I remember, I can do a comparison on the Condition_weight without doing too much on query.
My expectation query is something like this:
select Price from Table_1
where Type = 'A'
and {my_input_this_is a number} satisfy Condition_weight
I read it somewhere about this solution but cant find it again.
You can create a function that returns true - you will have to do the logic to extract min and max and compare value.
pseudo code...
CREATE FUNCTION conditionWeightIsSatisfed(number weight)
BEGIN
set #minValue = 0;
set #MaxValue = 1000;
..... do your conversion of the text values.....
select weight >= #minValue and weight <= #maxValue
END
For testing purposes I need to create a JSONB object with n random percentages, so that they sum up to 1.0.
Obviously, the very simple
SELECT jsonb_object(array_agg(ARRAY['prefix_' || n::TEXT, round(random()::NUMERIC, 2)::TEXT])) AS e
FROM generate_series(1,8) AS n
;
will produce numbers that won't sum up to 1.0.
I expect the solution to be much more complicated, and I can't seem to put my head around this.
How to do this in PostgreSQL 10?
You just have to adjust the values.
You could base your generator on this query:
WITH r AS (
SELECT random()
FROM generate_series(1, 8)
)
SELECT random/sum(random) OVER ()
FROM r;
WHAT I HAVE
I have a table with the following definition:
CREATE TABLE "Highlights"
(
id uuid,
chunks numeric[][]
)
WHAT I NEED TO DO
I need to query the data in the table using the following predicate:
... WHERE id = 'some uuid' and chunks[????????][1] > 10 chunks[????????][3] < 20
What should I put instead of [????????] in order to scan all items in the first dimension of the array?
Notes
I'm not entirely sure that chunks[][1] even close to something I need.
All I need is to test a row, whether its chunks column contains a two dimensional array, that has in any of its tuples some specific values.
May be there's better alternative, but this might do - you just go over first dimension of each array and testing your condition:
select *
from highlights as h
where
exists (
select
from generate_series(1, array_length(h.chunks, 1)) as tt(i)
where
-- your condition goes here
h.chunks[tt.i][1] > 10 and h.chunks[tt.i][3] < 20
)
db<>fiddle demo
update as #arie-r pointed out, it'd be better to use generate_subscripts function:
select *
from highlights as h
where
exists (
select *
from generate_subscripts(h.chunks, 1) as tt(i)
where
h.chunks[tt.i][3] = 6
)
db<>fiddle demo
SELECT * FROM table1 WHERE spent>= '1000'
This query still bring out numbers such as 598.99 and 230.909. My question is why is it doing this when I asked to search over or equal to 1000. Is there anyway to query so it only shows equal and more than 1000?
This happens because your '1000' is a text value. The other value is (or is converted to) text, too, so you end up with byte-per-byte comparison.
598.99 is greater then 1000 because 5... is greater then 1....
Cast to numeric types to do a proper comparison:
SELECT * FROM table1 WHERE spent::numeric >= '1000'::numeric
Or simply:
SELECT * FROM table1 WHERE spent::numeric >= 1000
You must compare numbers to get numeric comparison.
Use
WHERE CAST(spent AS numeric) >= 1000
How do I get the largest value in a column under a constant?
Specifically, in a table with a column of speed values how can I get the row with largest speed, under an arbitrary limit (say, 1200 mph)?
Thanks
Get a list of all the rows that fall below your maximum, then ORDER BY speed and LIMIT 1.
SELECT *
FROM your_table
WHERE speed < 1200
ORDER BY speed DESC
LIMIT 1;
If no row satisfies your criteria (i.e. the table is empty or every row has a speed larger than 1200), the query will return no rows. You should be prepared to handle this eventuality.
Unless I'm missing something, this is a simple max() with a where condition:
select max(speed)
from some_table
where speed < 1200;