I'm trying to wrap my head around how to do a proper subquery, it's not making sense to me, lets say I have two tables books and chapters:
Books
+----+------------------+----------+---------------------+
| id | name | author | last_great_chapters |
+----+------------------+----------+---------------------+
| 1 | some book title | john doe | 2 |
| 2 | foo novel title | some guy | 4 |
| 3 | other book title | lol man | 3 |
+----+------------------+----------+---------------------+
Chapters
+----+---------+----------------+
| id | book_id | chapter_number |
+----+---------+----------------+
| 1 | 1 | 1 |
| 2 | 1 | 3 |
| 3 | 1 | 4 |
| 4 | 1 | 5 |
| 5 | 2 | 1 |
| 6 | 2 | 2 |
| 7 | 2 | 3 |
| 8 | 2 | 4 |
| 9 | 2 | 5 |
| 10 | 3 | 1 |
| 11 | 3 | 2 |
| 12 | 3 | 3 |
| 13 | 3 | 4 |
| 14 | 3 | 5 |
+----+---------+----------------+
How can I join the two tables, and just print out the number of rows (sorted limit(last_great_chapters)) of the "last_great_chapters" from the books table list for each book?
if I understood correctly, you want to print out table books and last_great_chapters count in Chapters table?
if yes, try it
select b.id, b.name, b.author , b.last_great_chapter, COUNT(c.chapter_number) as rownumbers FROM Books as b
LEFT JOIN Chapters AS C ON c.chapter_number = b.last_great_chapters
group by b.id, b.name, b.author , b.last_great_chapter
Related
Hi i have a table like this;
+----+----------+-------------+
| id | room_id | house_id |
+----+----------+-------------+
| 1 | 1 | 1 |
| 2 | 2 | 1 |
| 3 | 3 | 1 |
| 4 | 1 | 2 |
| 5 | 2 | 2 |
| 6 | 3 | 2 |
| 7 | 1 | 3 |
| 8 | 2 | 3 |
| 9 | 3 | 3 |
+----+-------+----------------+
and i want to create a view like this
+----+----------+-------------+
| id | house_id | rooms |
+----+----------+-------------+
| 1 | 1 | [1,2,3] |
| 2 | 2 | [1,2,3] |
| 3 | 3 | [1,2,3] |
+----+-------+----------------+
i tried many ways but i cant gruop them in one line
Thanks for any help.
You can use array_agg():
select house_id, array_agg(room_id order by room_id) as rooms
from t
group by house_id;
If you want the first column to be incremental, you can use row_number():
select row_number() over (order by house_id) as id, . . .
I have a SQL table as following
--------------------------
| REPO | USER | FOLLOWER |
--------------------------
| A | 1 | 3 |
| A | 2 | 4 |
| A | 3 | 6 |
| B | 2 | 7 |
| B | 4 | 2 |
| C | 5 | 3 |
| C | 2 | 6 |
| C | 6 | 5 |
--------------------------
Now, I want to only those rows where USER follows another USER for
same REPO.
i.e. I want rows where elements in FOLLOWER is also in USER for same
REPO.
OUTPUT should be like...
--------------------------
| REPO | USER | FOLLOWER |
--------------------------
| A | 1 | 3 |
| B | 4 | 2 |
| C | 6 | 5 |
| C | 2 | 6 |
--------------------------
Thank You :)
One simple method uses exists:
select t.*
from t
where exists (select 1 from t t2 where t2.repo = t.repo and t2.follower = t.user);
Shouldn't the output actually be as follows, i.e. 4 rows?
--------------------------
| REPO | USER | FOLLOWER |
--------------------------
| A | 1 | 3 |
| B | 4 | 2 |
| C | 6 | 5 |
| C | 2 | 6 |
--------------------------
I have two tables, A and B, and a join table M. I want to, for each A.id, get the top 2 B.id's sorting on the value in table M, producing the results below. This is running on an Azure SQL database
Table A Table M Table B
+-----+ +-----+-----+-------+ +-----+
| Id | | AId | BId | Value | | Id |
+-----+ +-----+-----+-------+ +-----+
| 1 | | 1 | 3 | 4 | | 1 |
| 2 | | 1 | 2 | 3 | | 2 |
| 3 | | 3 | 2 | 3 | | 3 |
| 4 | | 3 | 5 | 6 | | 4 |
+-----+ | 3 | 3 | 4 | | 5 |
| 4 | 1 | 2 | +-----+
| 4 | 2 | 1 |
| 4 | 4 | 3 |
+-----+-----+-------+
Result
+-----+-----+-------+
| AId | BId | Value |
+-----+-----+-------+
| 1 | 3 | 4 |
| 1 | 2 | 3 |
| 3 | 5 | 6 |
| 3 | 3 | 4 |
| 4 | 1 | 2 |
| 4 | 4 | 3 |
+-----+-----+-------+
I know that I can select all the M.AId rows where they equal 1, sort it, and limit by 2, but I need to do this for every row in Table A. I've made an attempt to use group by, but I wasn't sure how to sort and limit it. I've also tried to search for resources associated with this issue but I couldn't find any resources.
(I also wasn't sure how to word the title for this issue)
You can just use ROW_NUMBER:
SELECT
AId, BId, Value
FROM (
SELECT *,
Rn = ROW_NUMBER() OVER(PARTITION BY AId ORDER BY Value DESC)
FROM M
) t
WHERE Rn <= 2
The scenario I am working on is as follows:-
A number of interviews are conducted a food poisoning case
A query called qryFoodInCase ( fldCaseID, fldFood) is generate consisting of all the food mentioned in all the interviews
An other query call qryFoodInInterview( fldCaseID, fldInterviewID, fldFood) consist of the food mentioned in each Interview
Now I am after the sql for a query that will return the food that was not consumed by an interviewee but consumed by one or more other interviewees.
The closest I've got is:
select Q1.fldCaseID,Q1.fldfood,Q2.fldInterviewID,fldGotSick
from qryFoodInCases as Q1
left join
(select * from qryFoodInInterview where qryFoodInInterview.fldInterviewID=1) as Q2
on Q1.fldFood=Q2.fldFood
where Q1.fldCaseID=1
The field Q2.fldInterviewID returns 1 for the food consumed and null for the food not consumed. However, I don't want to hard code the fldInterviewID in the sql. I would like a similar recordset returned for all the interviews in one query.
The SQL for qryFoodInCase and qryFoodInInterview are as follows:-
CREATE VIEW `qryFoodInCases`
AS
SELECT tblCases.fldCaseID
,fldfood
,count(tblFoodHistory.fldFoodID) AS fldFoodFrequency
FROM tblFood
INNER JOIN tblFoodHistory
ON tblFoodHistory.fldFoodID = tblFood.fldFoodID
INNER JOIN tblMealHistory
ON tblFoodHistory.fldMealID = tblMealHistory.fldMealHistoryID
INNER JOIN tblInterviews
ON tblInterviews.fldInterviewID = tblMealHistory.fldInterviewID
INNER JOIN tblCases
ON tblCases.fldCaseID = tblInterviews.fldCaseID
GROUP BY tblCases.fldCaseID, tblFood.fldFood
OUTPUT:
+-----------+------------+------------------+
| fldCaseID | fldFood | fldFoodFrequency |
+-----------+------------+------------------+
| 1 | Banana | 3 |
| 1 | Beans | 5 |
| 1 | Cabagge | 3 |
| 1 | Chicken | 1 |
| 1 | Pork | 5 |
| 1 | Potatoes | 1 |
| 1 | Rice | 1 |
| 1 | fried fish | 1 |
| 2 | Cabagge | 1 |
| 2 | Chicken | 2 |
| 2 | Potatoes | 1 |
| 2 | Rice | 1 |
| 2 | Salad | 1 |
+-----------+------------+------------------+
and
CREATE VIEW `qryFoodInInterview`
AS
SELECT tblInterviews.fldCaseID
,tblInterviews.fldInterviewID
,tblFood.fldFood
,tblInterviews.fldGotSick
FROM tblInterviews
INNER JOIN tblMealHistory
ON tblInterviews.fldInterviewID = tblMealHistory.fldInterviewID
INNER JOIN tblFoodHistory
ON tblFoodHistory.fldMealID = tblMealHistory.fldMealHistoryID
INNER JOIN tblFood
ON tblFood.fldFoodID = tblFoodHistory.fldFoodID
GROUP BY tblInterviews.fldInterviewID, tblFoodHistory.fldFoodID
OUTPUT
+-----------+----------------+------------+------------+
| fldCaseID | fldInterviewID | fldFood | fldGotSick |
+-----------+----------------+------------+------------+
| 1 | 1 | Pork | 0 |
| 1 | 1 | Banana | 0 |
| 1 | 1 | Rice | 0 |
| 1 | 1 | Potatoes | 0 |
| 1 | 2 | Chicken | 1 |
| 1 | 2 | Banana | 1 |
| 1 | 2 | Beans | 1 |
| 1 | 4 | Pork | 1 |
| 1 | 4 | fried fish | 1 |
| 1 | 4 | Beans | 1 |
| 2 | 6 | Salad | 0 |
| 2 | 6 | Chicken | 0 |
| 2 | 6 | Cabagge | 0 |
| 2 | 6 | Rice | 0 |
| 2 | 6 | Potatoes | 0 |
| 1 | 8 | Pork | 0 |
| 1 | 8 | Cabagge | 0 |
| 1 | 9 | Pork | 1 |
| 1 | 9 | Banana | 1 |
| 1 | 9 | Beans | 1 |
| 1 | 10 | Cabagge | 1 |
| 1 | 10 | Beans | 1 |
| 1 | 11 | Pork | 1 |
| 1 | 11 | Cabagge | 1 |
| 1 | 11 | Beans | 1 |
+-----------+----------------+------------+------------+
SQL Fiddle Demo
create a cross join off all food with all interviewrs
then a left join to see which one didnt had interview
the null mean interview didnt consume food
and exists mean someone different to interview consume food
.
SELECT F.fldFood, I.fldInterviewID, FI.fldInterviewID
FROM qryFoodInCases F, (SELECT DISTINCT fldInterviewID FROM qryFoodInInterview) I
LEFT JOIN qryFoodInInterview FI
ON F.fldFood = FI.fldFood
AND I.fldInterviewID = FI.fldInterviewID
WHERE FI.fldInterviewID IS NULL
AND EXISTS (SELECT 1
FROM qryFoodInInterview Q1
WHERE Q1.fldFood = F.fldFood
AND Q1.fldInterviewID <> I.fldInterviewID)
;
The trick was do the thing one step at the time. Once I realize I need all the combinations and create the cross join, the rest was easy.
select Q1.fldCaseID,Q1.fldfood,Q2.fldInterviewID,fldGotSick
from qryFoodInCases as Q1
left join
(select * from qryFoodInInterview QF1
JOIN qryFoodInInterview QF2
where QF1.fldInterviewID <> QF2.fldInterviewID
AND QF1.fldInterviewID > QF2.fldInterviewID
) as Q2
on Q1.fldFood=Q2.fldFood
where Q1.fldCaseID=1
As you mentioned you want to duplicate the items FoodInterviews, self JOIN will suffice your question. Please try this out , caution I didn't tested it.
Fixing Missed Self Join Condition to fix duplicates.
I trying to get the result table to contain rows where
Condition1: A.pc=B.pc AND
Condition2: (preferred (A.sub = B.Sub) or
else any one row that satisfy only Condition1)
I have tried the following inner join query and few other join and sub-query but can not figure out exact way to write a query with above strange condition.
SELECT * FROM tblA AS A INNER JOIN tblB AS B
ON A.sub=B.sub
WHERE A.pc=B.pc
tblA
-------------------
| id | pc | sub |
-------------------
| 0 | 5 | abc |
| 1 | 8 | def |
| 2 | 6 | ghi |
| 3 | 2 | jkl |
| 4 | 7 | mno |
| 5 | 19 | pqr |
-------------------
tblB
-------------------------
| pc | sub | uml | ull |
-------------------------
| 3 |arm | 1 | 1 |
| 3 |gtk | 1 | 2 |
| 3 |lmn | 1 | 3 |
| 3 |pop | 1 | 4 |
| 5 |abc | 1 | 5 |
| 5 |hlq | 1 | 6 |
| 5 |pon | 2 | 1 |
| 5 |qrt | 2 | 2 |
| 7 |alo | 2 | 3 |
| 7 |mno | 2 | 4 |
| 7 |ghm | 2 | 5 |
| 7 |stm | 2 | 6 |
| 9 |mck | 2 | 7 |
| 9 |plo | 3 | 1 |
| 9 |rtk | 3 | 2 |
| 9 |ert | 3 | 3 |
| 6 |gji | 3 | 4 |
| 6 |ghi | 3 | 5 |
| 6 |yux | 4 | 1 |
| 6 |del | 4 | 2 |
| 2 |jkl | 4 | 3 |
| 2 |jll | 5 | 4 |
| 2 |uin | 6 | 1 |
| 2 |tro | 6 | 2 |
| 19 |ppm | 6 | 3 |
| 19 |kde | 6 | 4 |
| 19 |grp | 6 | 5 |
| 19 |sho | 6 | 6 |
-------------------------
Expected Result Table:
-------------------------------
| id | pc | sub | uml | ull |
-------------------------------
| 0 | 5 |abc | 1 | 5 |
| 2 | 6 |ghi | 3 | 5 |
| 3 | 2 |jkl | 4 | 3 |
| 4 | 7 |mno | 2 | 4 |
| 5 | 19 |ppm | 6 | 3 | *
-------------------------------
* notice this is a arbitrary row as (A.sub=B.sub) not found
** notice there is no result for id=1 as pc=8 do not exist in tblB
Until someone comes up with a better answer, here is some code that does what you want.
Please, note it might not be a good solution in terms of performance (espcially as your tables grow).
SELECT *
FROM (
SELECT tblA.id, tblB.*
FROM tblA INNER JOIN tblB
ON tblA.pc = tblB.pc AND
tblA.id NOT IN (SELECT tblA.id
FROM tblA INNER JOIN tblB
ON tblA.sub = tblB.sub)
GROUP BY tblA.id
UNION
SELECT tblA.id, tblB.*
FROM tblA INNER JOIN tblB
ON tblA.sub = tblB.sub
GROUP BY tblA.id
) AS tu
ORDER BY id ASC;
See, also, this short demo.
One way of doing it I came up with is to repeat a join condition in where clause:
SELECT *
FROM tblA AS A
INNER JOIN tblB AS B
ON A.pc = B.pc
WHERE A.sub = B.sub
OR A.pc = B.pc