If I have a table...
ID Name Manager
0 Joe Sue
1 Jake Tom
0 Joe Tom
2 Larry Red
2 Larry Paul
1 Jake Paul
I want the output to be....
ID Name Manager1 Manager2
0 Joe Sue Tom
1 Jake Tom Paul
2 Larry Red Paul
Thanks...
If I have understood your request properly, yes, something like would produce the results you are looking for.
SELECT
t1.Name Name,
t1.Manager Manager1,
t2.Manager Manager2
FROM
Table t1
inner join Table t2 on t1.Manager = t2.Name
Of course a foreign key back to the index column would be preferential to strong comparisons for performance.
Yeah, if your table was called 'Managers':
SELECT Mgr1.ID,Mgr1.Name,Mgr1.Manager,Mgr2.Manager
FROM Managers AS Mgr1
LEFT JOIN Managers AS Mgr2
ON Mgr1.ID=Mgr2.ID
If your keeping the tables a join would be best.
If you hate joins, you could combine the max and min managers, and even then it would work if there is always 2 managers and they can't have the same name.
The below should work if I remember how to join up 2 queries correctly. but i would advise to see if it is possible to rework your table, have a separate table linking people to each other in a manager employee relation.
SELECT DISTINCT
F.ID, F.Name, S.Manager, F.Manager
FROM
(SELECT
ID, Name, MIN(manager) manager
FROM Managers
GROUP BY ID, Name) F,
(SELECT
ID, Name, MAX(manager) manager
FROM Managers
GROUP BY ID, Name) S
WHERE
F.ID = S.ID
AND S.Manager <> F.Manager
AND F.ID < S.ID
Related
How do I fill the null values in Table A using values from Table B while keeping all other columns/rows intact?
Table A
name
dept
job
jon
null
analyst
mary
null
supervisor
lucy
null
actuary
mark
retail
manager
cindy
retail
sales
Table B
name
dept
job
jon
hr
null
mary
hr
null
lucy
finance
null
attempts to use joins has incorrect results due to having to select which columns show in final table. ex:
SELECT a.name, b.dept, a.job
FROM table_a AS a
LEFT JOIN table_b AS b
ON a.name=b.name
will show
name
dept
job
jon
hr
analyst
mary
hr
supervisor
lucy
finance
actuary
mark
null
manager
cindy
null
sales
I've tried out different types of joins, but can't seem to figure it out. Thanks in advance!
Use COALESCE() to combine two values that could be null.
For example:
SELECT a.name,
coalesce(a.dept, b.dept) as dept,
coalesce(a.job, b.job) as job
FROM table_a AS a
LEFT JOIN table_b AS b
ON a.name=b.name
I have these two tables:
Table 1
Date Name StudentID TotalDuration
------------------------------------------------------------
2019-09-30 aA 11111 100
2019-09-30 bB 22222 40
2019-09-30 cC 33333 60
2019-10-07 aA 11111 50
2019-10-07 bB 22222 10
2019-10-07 cC 33333 12
2019-10-07 dD 44444 90
It contains data of students who ATTENDED a lecture (hence, does not include those who did not attend.
Table 2
StudentID Surname FirstName Group
------------------------------------------------------------
11111 A a 1
22222 B b 1
33333 C c 1
44444 D d 2
55555 E e 2
66666 F f 2
77777 G g 3
Table2 contains data of ALL students in the class.
Name attribute in Table 1 is combination of surname + first name and TotalDuration is duration of student participation in minutes.
I want to combine these two tables so that it list all the students in the class and their TotalDuration.
I tried OUTER JOIN and UNION ALL, but can't figure out how I can list all the student, yet shows NULL value for those students who did not attend to the lecture on particular date.
How can I achieve this?
You could left join and group by. But since you just need one aggregate computation, a correlated subquery is probably a simpler and more efficient approach (if you have the right index in place - see below):
select
t2.*,
(
select sum(totalduration)
from table1 t1
where t1.studentid = t2.studentid
) totalduration
from table2 t2
For performance, consider an index on table1(studentid, totalduration).
Side note: from a database design perspective, column Name in table1 is just not needed; this is redondant information, that complicates maintenance task (what if someone changes the first name of a studend in the other table?). You should remove that column, and rely on the foreign key on studentid only.
You probably want to aggregate the result by StudentID and use a LEFT JOIN, as in:
select
a.StudentId,
a.FirstName,
a.Surname,
a.Group,
sum(b.TotalDuration) as total_duration
from table2 a
left join table1 b on b.StudentId = a.StudentId
group by a.StudentId
Note that grouping by a.FirstName and a.Surname (assuming StudentId is the primary key) is optional according to the SQL Standard. I'm not sure SQL server will require it, though.
I have three tables STUDENTS, SUBJECTS, RANK ,with data as -
1) STUDENTS [NAME(Primary)]
NAME
--------
Alex
Greg
2) SUBJECTS [ID(Primary)]:
ID
--------
100
101
102
3) RANK [SEQ(Primary), NAME, ID, RANK]
SEQ NAME ID RANK
------ ------- ------ ------
1 Alex 100 A
2 Greg 100 A
3 Greg 101 B
I want to create a view that should display data as
NAME ID RANK
------- ------ ------
Alex 100 A
Alex 101 Z
Alex 102 Z
Greg 100 A
Greg 101 B
Greg 102 Z
So, for every student and for every subject, the View should display the RANK if present in RANK table, else replace the NULL with 'Z'.
I'm a newbie to SQL. So any help in forming the query would be deeply appreciated!
cross join student and subject then left outer join the result with rank to get ranks for all (student, subject) combination. selecting column with NVL OR COALESCE will replace NULL with 'z'.
SELECT st.name,
su.id,
NVL(ra.rank,'Z') Rank, --COALESCE(ra.rank,'Z') Rank
FROM student st
CROSS JOIN subject su
LEFT OUTER JOIN rank ra
ON ra.name = st.name
AND ra.id = su.id
ORDER BY st.name,su.id
Note : ORDER BY can be removed from above query if you don't need.
fiddle
SELECT r.NAME, r.ID, NVL(r.RANK, 'Z')
FROM RANK r, studendts st, SUBJECTS su
WHERE st. NAME = r. NAME
AND su.ID = r.ID
ORDER BY 1,2,3
Student
student_id FirstName LastName
---------------------------------------------------
1 Joe Bloggs
2 Alan Day
3 David Johnson
Student_Course
course_id student_id courseName
---------------------------------------------------
1 1 Computer Science
2 1 David Beckham Studies
3 1 Geography
1 3 Computer Science
3 3 Geography
Student_clubs
club_id student_id club_name club_count
---------------------------------------------------
1 1 Footbal 10
2 1 Rugby 10
3 1 Syncronized Swimming 10
4 3 Tennis 15
In the above example, student with id = 1 takes 3 course and is part of 3 clubs.
If i was to find out which courses a student is involved in or which club the student is part of i can do it but i will need to run two queries. Is it possible to run a single query against the
tables listed above so that the results come out like this:
Output
student_id FirstName Student_associated_courses Student_associated_clubs
---------------------------------------------------------------------------
1 Joe 1,2,3 Football, Rugby, Syncronized swimming
3 David 1,3 Tennis
Is it possible to get the above output with just one query? I am using JDBC to get the data so i am trying to see if i can avoid multiple trips to get the necessary data.
use GROUP_CONCAT with DISTINCT in MySQL
SELECT a.student_ID, a.firstname,
GROUP_CONCAT(DISTINCT b.course_ID),
GROUP_CONCAT(DISTINCT c.club_name)
FROM student a
INNER JOIN student_Course b
ON a.student_id = b.student_ID
INNER JOIN student_clubs c
ON a.student_ID = c.student_ID
GROUP BY a.student_ID, a.firstname
See SQLFiddle Demo
Try it like this:
SELECT *
FROM Student s JOIN
(SELECT sc."student_id", listagg(sc."course_id", ',')within group(ORDER BY sc."course_id")
FROM Student_Course sc
GROUP BY sc."student_id") s_course ON s."student_id"=s_course."student_id"
JOIN (SELECT sl."student_id", listagg(sl."club_name", ',')within GROUP(ORDER BY sl."club_name")
FROM Student_clubs sl
GROUP BY sl."student_id") s_club ON s."student_id"=s_club."student_id"
The "catch" is that LISTAGG doesn't work with DISTINCT keyword
Here is a fiddle
I have got a table named student. I have written this query:
select * From student where sname in ('rajesh','rohit','rajesh')
In the above query it's returning me two records; one matching 'rajesh' and another matching: 'rohit'.
But i want there to be 3 records: 2 for 'rajesh' and 1 for 'rohit'.
Please provide me some solution or tell me where i am missing.
NOTE: the count of result of sub query is not fix there can be many words there some distinct and some multiple occurrence .
Thanks
Your requirements are not clear, and I'll try to explain why.
Let's define table students
ID FirstName LastName
1 John Smith
2 Mike Smith
3 Ben Bray
4 John Bray
5 John Smith
6 Bill Lynch
7 Bill Smith
Query with WHERE clause:
FirstName in ('Mike', 'Ben', 'Mike')
will return 2 rows only, because it could be rewritten as:
FirstName='Mike' or FirstName='Ben' or FirstName='Mike'
WHERE is filtering clause that just says if existing row satisfy given conditions or not (for each of rows created by FROM clause.
Let's say we have subquery that returns any number of non distinct FirstNames
In case if SQ contains 'Mike', 'Ben', 'Mike' using inner join you can get those 3 rows without problem
Select ST.* from Students ST
Inner Join (Select name from …. <your subquery>) SQ
On ST.FirstName=SQ.name
Result will be:
ID FirstName LastName
2 Mike Smith
2 Mike Smith
3 Ben Bray
Note data are not ordered by order of names returning by SQ. If you want that, SQ should return some ordering number, eg.:
Ord Name
1. Mike
2. Ben
3. Mike
In that case query should be:
Select ST.* from Students ST
Inner Join (Select ord, name from …. <your subquery>) SQ
On ST.FirstName=SQ.name
Order By SQ.ord
And result:
ID FirstName LastName
2 Mike Smith (1)
3 Ben Bray (2)
2 Mike Smith (3)
Now, let's se what will happen if subquery returns
Ord Name
1. Mike
2. Bill
3. Mike
You will end up with
ID FirstName LastName
2 Mike Smith (1)
6 Bill Lynch (2)
7 Bill Smith (2)
2 Mike Smith (3)
Even worse, if you have something like:
Ord Name
1. John
2. Bill
3. John
Result is:
ID FirstName LastName
1 John Smith (1)
4 John Bray (1)
5 John Smith (1)
6 Bill Lynch (2)
7 Bill Smith (2)
1 John Smith (3)
4 John Bray (3)
5 John Smith (3)
This is an complex situation, and you have to clarify precisely what requirement is.
If you need only one student with the same name, for each of rows in SQ, you can use something like SQL 2005+):
;With st1 as
(
Select Row_Number() over (Partition by SQ.ord Order By ID) as rowNum,
ST.ID,
ST.FirstName,
ST.LastName,
SQ.ord
from Students ST
Inner Join (Select ord, name from …. <your subquery>) SQ
On ST.FirstName=SQ.name
)
Select ID, FirstName, LastName
From st1
Where rowNum=1 -- that was missing row, added later
Order By ord
It will return (for SQ values John, Bill, John)
ID FirstName LastName
1 John Smith (1)
6 Bill Lynch (2)
1 John Smith (3)
Note, numbers (1),(2),(3) are shown to display value of ord although they are not returned by query.
If you can split the where clause in your calling code, you could perform a UNION ALL on each clause.
SELECT * FROM Student WHERE sname = 'rajesh'
UNION ALL SELECT * FROM Student WHERE sname = 'rohit'
UNION ALL SELECT * FROM Student WHERE sname = 'rajesh'
Try using a JOIN:
SELECT ...
FROM Student s
INNER JOIN (
SELECT 'rajesh' AS sname
UNION ALL
SELECT 'rohit'
UNION ALL
SELECT 'rajesh') t ON s.sname = t.sname
just because you've got a criteria in there two times doesn't mean that it will return 1 result per criteria. SQL engines usually just use the unique criteria - thus, from your example, there will be 2 criteria in IN clause: 'rajesh','rohit'
WHY do you need to return 2 results? are there two rajesh in your table? they should BOTH return then. You don't need to ask for rajesh twice for that to happen. What does your data look like? What do you want to see returned?
Hi i am query just as you give above and it give me all data that matches in the condition of in clause. just like your post
select * from person
where personid in (
'Carson','Kim','Carson'
)
order by FirstName
and its give me all records which fulfill this Criteria