Consider this database structure:
__________ __________
| Trucks | | Mileage |
|__________|__________ |__________|________________________
| ID | DRIVER | | TRUCK_ID | MILEAGE | OIL_CHANGE |
|---------------------| |-----------------------------------|
| 1 | Tony | | 1 | 100000 105000 |
| 2 | George | | 2 | 6020 10020 |
| 3 | Mary | | 3 | 37798 41000 |
|_____________________| | 3 | 41233 47200 |
| 3 | 49000 |
|___________________________________|
I want to end up with a result set containing the maximum miles and maximum oil_change for each driver.
_________________________________
| 1 | Tony | 100000 | 105000 |
| 2 | George| 6020 | 10020 |
| 3 | Mary | 49000 | 47200 |
|_______________________________|
This is what I have tried so far:
SELECT t.*, MAX(m.mileage) AS mileage, MAX(m.oil_change) AS oil_change
FROM trucks t
LEFT JOIN mileage m ON t.id = m.truck_id
GROUP BY t.id
But this doesn't seem to allow the MAX function to work properly. It does not always contain the actual maximum value for mileage
Got it! Your mileage column must be defined as a character type, not a numeric type! When than happens, order is done alphabetically, not by value.
You should convert your mileage and oil_change columns to a numeric type (I'd recommend INT based on the data sample provided).
While you don't convert them, this will work:
SELECT t.*, MAX(cast(m.mileage as int)) AS mileage,
MAX(cast(m.oil_change as int)) AS oil_change
FROM trucks t
LEFT JOIN mileage m ON t.id = m.truck_id
GROUP BY t.id
The below queries should work for your question.
SELECT T.DRIVER,MIN(MILEAGE) AS MIN_MILEAGE,MIN(OIL_CHANGE) AS MIN_OIL_CHANGE
FROM TRUCKS T INNER JOIN MILEAGE M
ON T.ID = M.TRUCK_ID
GROUP BY T.DRIVER;
SELECT T.DRIVER,MAX(MILEAGE) AS MAX_MILEAGE,MAX(OIL_CHANGE) AS MAX_OIL_CHANGE
FROM TRUCKS T INNER JOIN MILEAGE M
ON T.ID = M.TRUCK_ID
GROUP BY T.DRIVER;
Regards
Venk
Related
I'm still working through some kinks with MySQL so any help will be appreciated.
I have 3 tables -- equipment, states, zones.
equipment:
+---------------+------+------------+
| current_state | id | ...columns |
+---------------+------+------------+
states:
+----------+-------------+
| state | zone_id |
+----------+-------------+
zones:
+-----+------+
| id | zone |
+-----+------+
In equipment, there is one current_state per row.
In states, there is one zone_id per row.
In zones, there is one zone per row.
I would like to JOIN the three tables as a subquery select statement (not even sure if that's a thing) and have the output return as 1 alias'd column among the other columns I'm selecting
+--------------+-------------+
| current_zone | ....columns |
+--------------+-------------+
A sample expected output is:
+------------+-------------+--------+------------------+--------------+---------+
| c_id | g_id | e_id | equipment_type | impressionId | email |
+------------+-------------+--------+------------------+--------------+---------+
| 1234 | ABC1234 | 0001 | VEST | 2032 |ab#yc.com|
| 1234 | 1234ABC | 0001 | SHIRT | 4372 |ab#yc.com|
| 1234 | DCBA123 | 0001 | CAN | 4372 |ab#yc.com|
| 1234 | DCBA321 | 0001 | JACKET | ab#yc.com |ab#yw.com|
| 4567 | abc321d | 0002 | SHIRT | 2032 |db#yw.com|
| 4567 | cba123d | 0002 | CAN | 4372 |db#yw.com|
| 4567 | def4rg4 | 0002 | JEANS | 3210 |db#yw.com|
+------------+-------------+--------+------------------+--------------+---------+
The current query has multiple joins already referring to the zones and states table in order to determine a different value:
SELECT equipment.*,
...
FROM equipment
LEFT JOIN c on equipment.c_id = c.id
LEFT JOIN g on equipment.g_id = g.id
LEFT JOIN states on g.state = states.state
LEFT JOIN zones on zones.id = states.zone_id
Essentially, what I want to do is create a subquery in order to create a new column based on the results of the three joins, something like this:
SELECT equipment.*,
(SELECT
equipment.current_state
FROM equipment
LEFT JOIN equipment.current_state = states.state
LEFT JOIN zones.id = states.zone_id
) as current_zone,
...
This is even possible? Am I trying to select a new column in the wrong place?
Thanks to #TheImpaler I was able to clear up my Scalar Subquery. In my eyes, I thought I had to create another join based on the properties I wanted when in reality all I had to do was create a conditional scalar subquery:
SELECT equipment.*,
(SELECT zones.zone
FROM zones
WHERE equipment.current_state = states.state
AND zones.id = states.zone_id
) as current_zone,
...
Context:
I'm attempting to take a series of market transactions, and determine the amount of money actually moving per item type. This is pretty much my first attempt at MySql, so the query is ugly, but the following nearly works:
SELECT types.typename,
averages.type,
averages.price,
movement.sold,
( averages.price * movement.sold ) AS value
FROM (SELECT type,
Round(Avg(price)) AS price
FROM orders
GROUP BY type) AS averages
INNER JOIN (SELECT type,
( startingvolume - currentvolume ) AS sold
FROM (SELECT type,
Sum(volume) AS currentVolume,
Sum(volumeentered) startingVolume
FROM orders
GROUP BY type) AS movement
WHERE ( startingvolume - currentvolume ) > 10000
ORDER BY sold) AS movement
ON averages.type = movement.type
INNER JOIN invtypes AS types
ON types.typeid = averages.type
ORDER BY value DESC
LIMIT 10 ;
-
+------------------------------------+-------+---------+------------+------------------+
| typeName | type | price | sold | value |
+------------------------------------+-------+---------+------------+------------------+
| Dirt | 34 | 1904767 | 2670581874 | 5086836224393358 |
| Light Wood | 2629 | 42999 | 2756595 | 118530828405 |
| Dark Wood | 24509 | 47344 | 1107771 | 52446310224 |
| Stone | 21922 | 18386 | 1505884 | 27687183224 |
| Grass | 238 | 5643 | 4554470 | 25700874210 |
| Paper | 3814 | 25635 | 861006 | 22071888810 |
| Iron | 3699 | 320270 | 58833 | 18842444910 |
| Ink | 16275 | 8552 | 2200545 | 18819060840 |
| Loam | 2679 | 5759 | 2608771 | 15023912189 |
| Copper | 672 | 904612 | 14989 | 13559229268 |
+------------------------------------+-------+---------+------------+------------------+
The problem with the data above is that the raw market data is unavoidably corrupted by outliers, as you can see below:
select type, price from orders where type = 34 order by price desc limit 10;
-
+------+-----------+
| type | price |
+------+-----------+
| 34 | 200000000 |
| 34 | 15.99 |
| 34 | 12.06 |
| 34 | 10 |
| 34 | 7.67 |
| 34 | 7.5 |
| 34 | 7.3 |
| 34 | 7.17 |
| 34 | 7.1 |
| 34 | 7.06 |
+------+-----------+
Core problem:
99% of the market data is clean, but the outliers destroy the average, and MySql doesn't seem to have a median function. I've found several examples of how to find the median of an entire column, but I need the median per-item.
How would I determine a per-item median in stead of a per-item mean, or efficiently clean the data of these outliers prior to running the primary query?
Note:
I've tried omitting results via std, but prices of items range from $17 to $10B, while deviation remains relatively low, regardless of price range.
I won't touch your original query because it very complex, but one option you could do would be to use a subquery to remove any statistical outliers. For example, if you wanted to remove any outlier from the orders table whose value is more than say two standard deviations away from the mean you could use:
SELECT t1.type,
t1.price
FROM orders t1
INNER JOIN
(
SELECT type,
AVG(price) AS AVG,
STD(price) AS STD
FROM orders
GROUP BY type
) t2
ON t1.type = t2.type
WHERE t1.price < ABS(2*t2.STD - t2.AVG) -- any value more than 2 standard devations
-- away from the mean is discarded
Demo here:
SQLFiddle
currently i have two tables with some data. the first table has the following:
+----------------+-----------+
| name | member_id |
+----------------+-----------+
| Juice Box | 49432 |
| Rainsurge | 49631 |
| spiderpigrider | 50482 |
+----------------+-----------+
The second table has the following:
+------------+-----------+
| recruit_id | bin(refs) |
+------------+-----------+
| 49432 | 1 |
| 49631 | 1 |
| 49432 | 1 |
| 49631 | 1 |
| 49432 | 1 |
| 49631 | 1 |
| 49432 | 1 |
| 49631 | 1 |
| 49432 | 1 |
| 49631 | 1 |
+------------+-----------+
I would like to return the name, total refs and member_id/recruit_id like so (listing only users with at least 1 ref)
+------------+-----------+------------+
| recruit_id | name | total_refs |
+------------+-----------+------------+
| 49631 | Rainsurge | 5 |
| 49432 | Juice Box | 5 |
+------------+-----------+------------+
select r.recruit_id,bin(r.refs),ipb.name from refs as r
inner join syndicate_ipb.core_members as ipb on ipb.member_id=r.recruit_id;
this returned my data but obviously without a total count and repeated names/ids
select r.recruit_id,count(bin(r.refs)),ipb.name from refs as r
inner join syndicate_ipb.core_members as ipb on ipb.member_id=r.recruit_id;
this returned data with the total count of everyone but only one id/name
+------------+--------------------+-----------+
| recruit_id | count(bin(r.refs)) | name |
+------------+--------------------+-----------+
| 49432 | 10 | Juice Box |
+------------+--------------------+-----------+
this returns the data but again without a count
select distinct r.recruit_id,bin(r.refs),ipb.name from refs as r
inner join syndicate_ipb.core_members as ipb on ipb.member_id=r.recruit_id;
+------------+-------------+-----------+
| recruit_id | bin(r.refs) | name |
+------------+-------------+-----------+
| 49432 | 1 | Juice Box |
| 49631 | 1 | Rainsurge |
+------------+-------------+-----------+
Any help or guidance is greatly appreciated. I feel like i'm close here but just not competent enough with SQL to get it. thanks!
You were almost there. You just missed the GROUP BY clause at the end.
Query:
SELECT
r.recruit_id,
count(bin(r.refs)),
ipb.name
FROM refs AS r
INNER JOIN syndicate_ipb.core_members AS ipb
ON ipb.member_id = r.recruit_id
GROUP BY r.recruit_id;
Note:
If bin(refs) column always contains value 1 then actually you don't need to keep that column. In that case you can use count(*) or count(r.recruit_id) to get the count.
And if bin(refs) column contains any value then count will not give you the right answer. In that case you need to use sum like Sum( bin(refs)).
You have to use the group by clause:
select r.recruit_id, ipb.name, count(bin(refs)) as total_refs
from refs as r
inner join syndicate_ipb.core_members as ipb
on ipb.member_id=r.recruit_id
group by r.recruit_id, ipb.name
having count(bin(refs)) >= 1
This group by r.recruit_id, ipb.name will group the results and this having count(bin(refs)) >= 1 will garante that it only returns members with at least one ref
Do not only group your columns just by the ones you want. Even though MySql allows it, it is not SQL Ansi pattern and even MySql now is complying with it. Use an aggregation function grouping with your entire columns on the select statement.
SELECT ipb.*, COUNT(`r`.`recruit_id`) AS cid FROM `ipb`
INNER JOIN `r` ON `r`.`join_id` = ipb.`member_id`
GROUP BY ipb.`member_id`
I'm having BookTable in database (with foregin hey LibID):
| BookID | BookName | BookPrice | LibID |
-------------------------------------------
| 1 | Book_1 | 200 | 1 |
| 2 | Book_2 | 100 | 1 |
| 3 | Book_3 | 300 | 2 |
| 4 | Book_4 | 150 | 4 |
and also LibraryTable:
| LibID | LibName | LibLocation |
-----------------------------------
| 1 | Lib_1 | Loc_1 |
| 2 | Lib_2 | Loc_2 |
| 3 | Lib_3 | Loc_3 |
| 4 | Lib_4 | Loc_4 |
I need to write SQL query that will return be the info about the library and number of books for that library:
| LibID | LibName | NumberOfBooks|
------------------------------------
| 1 | Lib_1 | 2 |
| 2 | Lib_2 | 1 |
| 3 | Lib_3 | 0 |
| 4 | Lib_4 | 1 |
It should be one SQL query, probably with nested queries or joins.. Not sure how the query should look like:
SELECT L.LibID AS LibID, L.LibName AS LibName, COUNT(B) AS NumberOfBooks
FROM LibraryTable L, BookTable B
WHERE L.LibID = B.LibID
Will that work?
No, this query will not work. COUNT aggregates data, so you must explicitely tell the DBMS for which group of data you want the count. In your case this is the library (you want one result record per library).
COUNT's parameter is a column, not a table, so change this to * (i.e. count records) or a certain column (e.g. LibID).
The join syntax you are using is valid, but deprecated. Use explicit joins instead. In your case an outer join would even show libraries that have no books at all, if such is possible.
select l.libid, l.libname, count(b.libid) as numberofbooks
from librarytable l
left outer join booktable b on b.libid = l.libid
group by l.libid;
You could also do all this without a join at all and get the book count in a subquery instead. Then you wouldn't have to aggregate. That's way simpler and more readable in my opinion.
select
l.libid,
l.libname,
(select count(*) booktable b where b.libid = l.libid) as numberofbooks
from librarytable l;
SELECT lt.LibID AS LibID, lt.LibName AS LibName, count(*) AS NumberOfBooks
FROM BookTable AS bt
LEFT JOIN LibraryTable AS lt ON bt.LibID = lt.LibID
GROUP BY bt.LibID
I've been staring at so much SQL code my brain is practically mush.
I'll make it quick. Below are my table structures, with irrelevant columns omitted:
attendance_history: member_info:
_____________________ ________________________
| Date | ID | | ID | Design Team |
|----------|--------| |--------|-------------|
| 1/27 | 1 | | 1 | DT1 |
| 1/28 | 1 | | 2 | DT2 |
| 1/29 | 2 | | 3 | DT2 |
| 1/29 | 3 | |--------|-------------|
|----------|--------|
My ultimate goal is to get an attendance average for every design team. But I believe I have all of the logic worked out except one part: I need to get the number of attendees for EACH design team for EACH date.
Here is an example of what I need:
__________________________________
| Date | Design Team | Count |
|----------|-------------|-------|
| 1/27 | DT1 | 1 |
| 1/28 | DT1 | 1 |
| 1/29 | DT1 | 0 |
| 1/27 | DT2 | 0 |
| 1/28 | DT2 | 0 |
| 1/29 | DT2 | 2 |
|----------|-------------|-------|
Any clues as to how I can achieve this? Currently I have a ridiculously long script that only gets the counts for the design teams if someone was present. I need somehow get a 0 for a count in a row if there was nobody present for that day from that team.
Thanks a ton, as always.
To get the zeros requires a bit of trickery. You need to generate all the rows first (using a cross join) and then left join in the attendance information:
select d.date, dt.design_team, coalesce(ddt.cnt, 0) as cnt
from (select distinct design_team from member_info) dt cross join
(select distinct date from attendance_history) d left outer join
(select ah.date, mi.design_team, count(*) as cnt
from attendance_history ah join
member_info mi
on ah.id = mi.id
group by ah.date, mi.design_team
) ddt
on ddt.design_team = dt.design_team and ddt.date = d.date;
Edit: Fixed subquery to join on ah.id = mi.id instead of ah.id = ah.id.