I have a MySQL table which looks like this:
id load_transit load_standby hours_transit hours_standby
1 40 20 8 4
2 30 15 10 10
3 50 10 3 9
I need to do the following calculations:
(intermediate calculations)
hours_transit_total = 8+10+3 = 21
hours_standby_total = 4+10+9 = 23
(desired result)
load_transit_weighted_mean = 40*(8/21) + 30*(10/21) + 50*(3/21) = 36.667
load_standby_weighted_mean = 20*(4/23) + 15*(10/23) + 10*(9/23) = 13.913
Is it possible to do this in a single query? What would the best design be?
Note that
40*(8/21) + 30*(10/21) + 50*(3/21) =
(40*8)/21 + (30*10)/21 + (50*3)/21 =
(40*8 + 30*10 + 50*3)/21
and
20*(4/23) + 15*(10/23) + 10*(9/23) =
(20*4)/23 + (15*10)/23 + (10*9)/23 =
(20*4 + 15*10 + 10*9)/23
Which allows you to get the results you want using
SELECT sum(hours_transit * load_transit) / sum(hours_transit),
sum(hours_standby * load_standby) / sum(hours_standby)
FROM your_table
I just had this same question and built this little query I think makes it clear how to find the weighted average in a single query:
select sum(balance), sum(rate * balance / 5200) as weighted_rate, -- what I want
-- what you cannot do: sum(rate * balance / sum(balance))
sum(balance * rate) / sum(balance) as weighted_rate_legit -- ah thank you transitive math properties
from (
select '4600' as balance, '2.05' as rate from dual
union all
select '600' as balance, '2.30' as rate from dual
) an_alias;
Related
I'm using MySQL version: 5.7.22
I've got two columns Latitude and Longitude both in Degrees/Minutes/Seconds format that I want to convert to Decimal format ex: 48° 52.250' N to 48.93611111
I have the following script but I'm stuck at how to split the degrees minutes and seconds. I cannot hard-code the values as I've done here left(Latitude,2) since the degrees might have 3 decimals as well
SELECT Latitude,
left(Latitude, 2) +
(TRUNCATE((Latitude - TRUNCATE(Latitude)) * 100) / 60) +
(((Latitude * 100) - TRUNCATE(Latitude * 100)) * 100) / (60 * 60) AS DECIMAL_DEGREES
FROM small_ocean_data
The formula for the conversion is this: D + M/60 + S/3600 * -1 if direction in ['W', 'S'] else 1
Any help would be grateful!
Well if I use this formula of yours: D + M/60 + S/3600
Where I believe D is Degrees and M are Minutes and S are Seconds.
With this select:
select SUBSTRING_INDEX('48° 52.250', '°',1) +
(SUBSTRING_INDEX('48° 52.250',' ',1)/60) +
(SUBSTRING_INDEX('48° 52.250','.',1)/3600);
Or for your database:
select SUBSTRING_INDEX(Latitude, '°', 1) +
(SUBSTRING_INDEX(Latitude ,' ',1)/60) +
(SUBSTRING_INDEX(Latitude ,'.',1)/3600) "DECIMAL_DEGREES"
FROM small_ocean_data;
I get 48.81333333333333
48 + 0.8 + 0.013333333333333334
Here is the DEMO
Assume a service is billed in the following manner:
The first 60 seconds is charged at $1.00
Subsequent charges are billed at $0.25 per 10 second
The following are example computations:
32 seconds = $1.00
59 seconds = $1.00
60 seconds = $1.00
61 seconds = $1.25
69 seconds = $1.25
70 seconds = $1.25
71 seconds = $1.50
Is it possible to do this kind of computation in MySQL alone?
EDIT 1:
Does something like this work:
SELECT `call_length`,
( 1.00 + ( Round(( `call_length` - 30 ) / 10) * .25 ) ) AS `cost`
FROM `service`
SqlFiddleDemo
CREATE TABLE sec(val INT);
INSERT INTO sec
VALUES (32), (59), (60), (61), (69), (70), (71);
SELECT
val,
1.0 + CASE
WHEN val <= 60.0 THEN 0
WHEN val MOD 10 = 0 THEN 0.25 *((val - 60) DIV 10)
ELSE 0.25 * (((val - 60) DIV 10) + 1)
END AS charge
FROM sec;
EDIT:
Without CASE:
SqlFiddleDemo2
SELECT
call_length,
1.0 + IF( call_length <= 60, 0, 0.25 * CEIL((call_length - 60)/10)) AS cost
FROM service;
This is not much of a MySQL problem, unless the setting in which you need to perform the calculation is somehow difficult(?).
UPDATE ... SET cost_cents = 100 + CEIL(GREATEST(0, duration - 60)/10) * 25;
As a SELECT to match your edit,
SELECT `call_length`,
100 + CEIL(GREATEST(0, `call_length` - 60)/10) * 25 AS `cost`
FROM `service`
Note that this returns cents. For dollars, divide the result by 100...
SELECT `call_length`,
(100 + CEIL(GREATEST(0, `call_length` - 60)/10) * 25) / 100 AS `cost`
FROM `service`
I want to convert feet and inches to centimeters format
Format in my DB is:
4'6" (4 feet, 6 inches)
Formula for converting into centimeters
4*30.48 = 121.92 (convert feet to centimeters = multiply by 30.48)
6*2.54 = 15.24 (convert inches to centimeters = multiply by 2.54)
So Result = 121.92 + 15.24 = 137.16 cm
eg:
Actual Table: inches
SELECT * FROM inches
id height
1 4'6"
2 4'7"
3 5'8"
4 5'9"
I expect the following result as centimeters when I do SQL query
id height
1 137.16
2 139.7
3 172.72
4 175.26
Thanks in advance :)
Probably far easier to do on the application level, but if you really had to, you could do it in SQL like this, using the SUBSTR and INSTR functions, and some basic math:
SET #height = '4''6"';
SELECT
SUBSTR(#height, 1, INSTR(#height, '''') - 1) * 12 * 2.54 +
SUBSTR(#height, INSTR(#height, '''') + 1, INSTR(#height, '"') - INSTR(#height, '''') - 1) * 2.54;
-- yields 137.16
Or, applied to your table structure:
SELECT id,
SUBSTR(height, 1, INSTR(height, '''') - 1) * 12 * 2.54 +
SUBSTR(height, INSTR(height, '''') + 1, INSTR(height, '"') - INSTR(height, '''') - 1) * 2.54 AS height
FROM inches;
Application side process will be better,
However,
SELECT
(CAST(SUBSTR(height,1, LOCATE("'",height)-1) AS UNSIGNED) * 30.48) +
(CAST(SUBSTR(height, LOCATE("'",height)+1) AS UNSIGNED) * 2.54 ) AS cm
FROM
inches;
I have a table with columns showing ranges, like
id from to
1 10 100
2 200 300
I have a query which will be a list of values, like 17, 20, 44, 288 etc.
Is it possible to have a result set which would include the where condition, so I get:
id from to input
1 10 100 7
1 10 100 20
1 10 100 144
2 200 300 288
Right now the code runs one query per where value and it works, and I'm looking to increase performance by combing it into one large multiple where clause, like
SELECT *
FROM table
WHERE (from<=7 AND start>=7)
OR (from<=20 AND start>=20)
OR (from<=144 AND start>=144)
OR (from<=288 AND start>=288)
What you want makes no sense regarding ranges.
7 and 144 has no compatible range yet you want to put then into the first range.
In a result set with lots of values listing you will probably get to many conditions.
What you can do is to put those values that isn't in a range to show without correspondence. Like this:
With the structure being:
create table test (
id integer,
vfrom integer,
vto integer
);
insert into test values
(1, 10, 100),
(2, 200, 300);
create table vals(
val integer
);
insert into vals values (7), (20), (144), (288);
You can use this query:
select val, id, vfrom, vto
from vals v left join
test t on ( t.vfrom <= v.val and t.vto >= v.val )
It will bring you:
7 null null null
20 1 10 100
144 null null null
288 2 200 300
see it here on fiddle: http://sqlfiddle.com/#!2/f68fd/8
Maybe it isn't what you want but it is more logical.
Sure there is a query for this. Trouble is we need a table for specific values to show up; and then there are sub-queries and union selects:
SELECT table.*, values.val AS input
FROM (SELECT 7 AS val UNION SELECT 20 AS val UNION SELECT 144 AS val UNION SELECT 288 AS val) as values
JOIN table ON table.from <= values.val AND table.to >= values.val
This should do the trick. Note that you only have to specify the column name in the first SELECT with in a UNION SELECT.
I will suppose you are using Java as your application language. You could build your query this way:
public String buildQuery(int[] myList) {
String queryToReturn = "";
for (int queryIndex = 0; queryIndex < myList.length; queryIndex++) {
queryToReturn += ((queryIndex == 0) ? ("") : (" union ")) +
"(select `id`, `from`, `to`, " + myList[queryIndex] + " as input
from MyTable
where `from` < " + myList[queryIndex] + " and " + myList[queryIndex] " < `to`)";
}
return queryToReturn;
}
Then run the returned query.
I have a field on my table which represents seconds, I want to convert to minutes
Select (100/60) as Minute from MyTable
-> 1.66
How can I get 1 minute and 40 seconds 00:01:40 and then round to 00:02:00 and if 00:01:23 round to 00:01:30
Using Mysql.
There are two ways of rounding, using integer arithmetic and avoiding floating points, a value to the nearest thirty seconds...
((seconds + 15) DIV 30) * 30
(seconds + 15) - (seconds + 15) % 30
The latter is longer, but in terms of cpu time should be faster.
You can then use SEC_TO_TIME(seconds) to get the format hh:mm:ss, and take the right 5 characters if you really need hh:mm.
If you wanted to avoid SEC_TO_TIME(seconds), you can build up the string yourself.
minutes = total_seconds DIV 60
seconds = total_seconds % 60
final string = LPAD(minutes, 2, '0') | ':' | LPAD(seconds, 2, '0')
i am not sure about how to round it but you can convert seconds into time i.e hh:mm:ss format using SEC_TO_TIME(totaltime)
Desired result :
A = 30
B = 60
C = 90
D = 120
select
(25 + 15)-(25 + 15) % 30 as A,
(32 + 15)-(32 + 15) % 30 as B,
(90 + 15)-(90 + 15) % 30 as C,
(100 + 15)-(100 + 15) % 30 as D
Result :
A = 30
B = 30
C = 90
D = 90
I try with this:
select
30* ceil(30/30) as A,
30* ceil(32/30) as B,
30* ceil(90/30) as C,
30* ceil(100/30) as D
Result :
A = 30
B = 60
C = 90
D = 120
Thank you for your help !
You can simply write your own function http://dev.mysql.com/doc/refman/5.0/en/create-procedure.html
But I'd rather do that in a programing language (PHP, Python, C), not on the database side.