I have a table with student info [STU] and a table with parent info [PAR]. I want to return an email address for each student, but just one. So I run this query:
SELECT [STU].[ID], [PAR].[EM]
FROM (SELECT [STU].* FROM DB1.STU)
STU LEFT JOIN (SELECT [PAR].* FROM DB1.PAR) PAR ON [STU].[ID] = [PAR].[ID]
This gives me the below table:
Student ID ParentEmail
1 jim#email.com
1 sarah#email.com
2 paul#email.com
2 tim#email.com
3 bill#email.com
3 frank#email.com
3 joyce#email.com
4 greg#email.com
5 tony#email.com
5 sam#email.com
Each student has multiple parent emails, but I only want one. In other words, I want the output to look like this:
Student ID ParentEmail
1 jim#email.com
2 paul#email.com
3 frank#email.com
4 greg#email.com
5 sam#email.com
I've tried so many things. I've tried using GROUP BY and MIN/MAX and I've tried complex CASE statements, and I've tried COALESCE but I just can't seem to figure it out.
I think OUTER APPLY is the simplest method:
SELECT [STU].[ID], [PAR].[EM]
FROM DB1.STU OUTER APPLY
(SELECT TOP (1) [PAR].*
FROM DB1.PAR
WHERE [STU].[ID] = [PAR].[ID]
) PAR;
Normally, there would be an ORDER BY in the subquery, to give you control over which email you want -- the longest, shortest, oldest, or whatever. Without an ORDER BY it returns just one email, which is what you are asking for.
If you just want one column from the parent table, a simple approach is a correlated subquery:
select
s.id student_id,
(select max(p.em) from db1.par p where p.id = s.id) parent_email
from db1.stu s
This gives you the greatest parent email per student.
Related
thanks in advance for any help on this, I am a bit of a newbie to MS SQL and I want to do something that I think is achievable but don't have the know how.
I have a simple table called "suppliers" where I can do (SELECT id, name FROM suppliers ORDER BY id ASC)
id
name
1
ACME
2
First Stop Business Supplies
3
All in One Supply Warehouse
4
Farm First Supplies
I have another table called "products"
id
name
supplier_id
1
Item 1
2
2
Item 2
1
3
Item 3
1
4
Item 4
3
5
Item 5
2
I want to list all the suppliers and get the total amount of products for each supplier if that makes sense on the same row? I am just not sure how to pass the suppliers.id through the query to get the count.
I am hoping to get to this:
id
name
total_products
1
ACME
2
2
First Stop Business Supplies
2
3
All in One Supply Warehouse
1
4
Farm First Supplies
0
I really appreciate any help on this.
Three concepts to grasp here. Left Join, group by, and Count().
select s.id, s.name, Count(*) as total_products
from suppliers s
left join products p on s.id=p.supplier_id --the left join gets your no matches
group by s.id, s.name
left join is a join where all of the values from the first table are kept even if there are no matches in the second.
Group by is an aggregation tool where the columns to be aggregated are entered.
Count() is simply a count of transactions for the grouped columns.
Try this :-
SELECT id, name, C.total_products
FROM Suppliers S
OUTER APPLY (
SELECT Count(id) AS total_products
FROM Products P
WHERE P.supplier_id = S.id
) C
I'm trying to do an inner join in a nested select statement. Basically, There are first and last reason IDs that produce a certain number (EX: 200). In another table, there are definitions for the IDs. I'm trying to pull the Last ID, along with the corresponding comment for whatever is pulled (EX: 200 - Patient Cancelled), then the first ID and the comment for whatever ID it is.
This is what I have so far:
Select BUSN_ID
AREA_NAME
DATE
AREA_STATUS
(Select B.REASON_ID
A.LAST_REASON_ID
FROM BUSN_INFO A, BUSN_REASONS B
WHERE A.LAST_REASON _ID=B.REASON_ID,
(Select B.REASON_ID
A. FIRST_REASON_ID
FROM BUSN_INFO A, BUSN_REASONS B
WHERE A_FIRST_REASON_ID = B.REASON_ID)
FROM BUSN_INFO
I believe an inner join is best, but I'm stuck on how it would actually work.
Required result would look like (this is example dummy data):
First ID -- Busn Reason -- Last ID -- Busn Reason
1 Patient Sick 2 Patient Cancelled
2 Patient Cancelled 2 Patient Cancelled
3 Patient No Show 1 Patient Sick
Justin_Cave's SECOND example is the way I used to solve this problem.
If you want to use inline select statements, your inline select has to select a single column and should just join back to the table that is the basis of your query. In the query you posted, you're selecting the same numeric identifier multiple times. My guess is that you really want to query a string column from the lookup table-- I'll assume that the column is called reason_description
Select BUSN_ID,
AREA_NAME,
DATE,
AREA_STATUS,
a.last_reason_id,
(Select B.REASON_description
FROM BUSN_REASONS B
WHERE A.LAST_REASON_ID=B.REASON_ID),
a.first_reason_id,
(Select B.REASON_description
FROM BUSN_REASONS B
WHERE A.FIRST_REASON_ID = B.REASON_ID)
FROM BUSN_INFO A
More conventionally, though, you'd just join to the busn_reasons table twice
SELECT i.busn_id,
i.area_name,
i.date,
i.area_status,
i.last_reason_id,
last_reason.reason_description,
i.first_reason_id,
first_reason.reason_description
FROM busn_info i
JOIN busn_reason first_reason
ON( i.first_reason_id = first_reason.reason_id )
JOIN busn_reason last_reason
ON( i.last_reason_id = last_reason.reason_id )
I was trying to update table columns from another table.
In person table, there can be multiple contact persons with same inst_id.
I have a firm table, which will have latest 2 contact details from person table.
I am expecting the firm tables as below:
If there is only one contact person, update person1 and email1. If there are 2, update both. If there is 3, discard the 3rd one.
Can someone help me on this?
This should work:
;with cte (rn, id, inst_id, person_name, email) as (
select row_number() over (partition by inst_id order by id) rn, *
from person
)
update f
set
person1 = cte1.person_name,
email1 = cte1.email,
person2 = cte2.person_name,
email2 = cte2.email
from firm f
left join cte cte1 on f.inst_id = cte1.inst_id and cte1.rn = 1
left join cte cte2 on f.inst_id = cte2.inst_id and cte2.rn = 2
The common table expression (cte) used as a source for the update numbers rows in the person table, partitioned by inst_id, and then the update joins the cte twice (for top 1 and top 2).
Sample SQL Fiddle
I think you don't have to bother yourself with this update, if you rethink your database structure. One great advantage of relational databases is, that you don't need to store the same data several times in several tables, but have one single table for one kind of data (like the person's table in your case) and then reference it (by relationships or foreign keys for example).
So what does this mean for your example? I suggest, to create a institution's table where you insert two attributes like contactperson1 and contactperson2: but dont't insert all the contact details (like email and name), just the primary key of the person and make it a foreign key.
So you got a table 'Person', that should look something like this:
ID INSTITUTION_ID NAME EMAIL
1 100 abc abc#inst.com
2 101 efg efg#xym.com
3 101 ijk ijk#fg.com
4 101 rtw rtw#rtw.com
...
And a table "Institution" like:
ID CONTACTPERSON1 CONTACTPERSON2
100 1 NULL
101 2 3
...
If you now want to change the email adress, just update the person's table. You don't need to update the firm's table.
And how do you get your desired "table" with the two contact persons' details? Just make a query:
SELECT i.id, p1.name, p1.email, p2.name, p2.email
FROM institution i LEFT OUTER JOIN person p1 ON (i.contactperson1 = p1.id)
LEFT OUTER JOIN person p2 ON (i.contactperson2 = p2.id)
If you need this query often and access it like a "table" just store it as a view.
Can anyone help me fetch the non matching rows from two tables in Oracle?
Table: Names
Class_id Stud_name
S001 JAMES
S001 PETER
S002 MARK
Table: Course
Course_id Stud_name
S001 JAMES
S001 KEITH
S002 MARK
Output
I need the rows to display as
CLASS ID STUD_NAME_FROM_NAME_TABLE STUD_NAME_FROM_COURSE_TABLE
---------------------------------------------------------------------
S001 PETER KEITH
I have used Oracle joins to fetch the non matching names:
SELECT *
FROM Names, Course
WHERE Names.Class_id=Course.Course_id
AND Names.Stud_name<>Course.Stud_name
This query is returning duplicate rows.
If you insist on Join you can use this one:
SELECT *
FROM Names
FULL OUTER JOIN Course ON Names.Class_id=Course.Course_id
AND Names.Stud_name = Course.Stud_name
WHERE Names.Stud_name IS NULL or Course.Stud_name IS NULL
Fetches unmatched rows in Names table
SELECT * FROM Names
WHERE
NOT EXISTS
(SELECT 'x' from Course
WHERE
Names.Class_id = Course.Course_id AND
Names.Stud_name = Course.Stud_name)
Fetches unmatched rows in Names and Course too!
SELECT Names.Class_id,Names.Stud_name,C1.Stud_name
FROM Names , Course C1
WHERE Names.Class_id = C1.Course_id AND
NOT EXISTS
(SELECT 'x' from Course C2
WHERE
Names.Class_id = C2.Course_id AND
Names.Stud_name = C2.Stud_name);
When you ask for unmatching rows I assume that you want rows that exist in names but not in course.
If this is the case you're probably after
select * from names
where (class_id, stud_name ) not in
(select course_id, stud_name from course);
Your query returned duplicate rows beacuse for each row in names it selected all rows in course that satisfied the where condition.
So, for the row S001, PETER in names it faound that S001, JAMES and S001, KEITH matched that condition, thus, that row was "returned" twice.
EDIT Since it is not clear if stud_name is a primary key, or unique (and on second sight I think it's not), you'd probably want a
select * from names
where not exists (
select 1 from course where
names.class_id = course.course_id and
names.stud_name <> course.stud_name
)
Edit II if you insist on using a join (as per your comment) you might want to try a
select distinct names.* from...
Hope it helps you
with not_in_class as
(select a.*
from Names a
where not exists ( select 'x'
from course b
where b.Course_id = a.class_id
and a.Stud_name = b.Stud_name)),
not_in_course as
(select b.*
from course b
where not exists ( select 'x'
from Names a
where b.Course_id = a.class_id
and a.Stud_name = b.Stud_name))
select x.class_id,
x.Stud_name NOT_IN_CLASS,
y.stud_name NOT_IN_COURSE
from not_in_class x, not_in_course y
where x.class_id = y.course_id
Output
| CLASS_ID | NOT_IN_CLASS | NOT_IN_COURSE |
|----------|--------------|---------------|
| S001 | PETER | KEITH |
Only problem is that if multiple mismatches are there in both the tables for a given id, it works for single mismatch for a particular id. You need to rework if multiple mismatches are there for the same id.
Well, I am not sure if I understand correctly what you are asking. I think you want a list of all IDs where the student list in class table and course table differs. Then you want to show the id and the students that are in class but not in course and the students that are in course but not in class.
To do so you would full outer join the tables. That gives you students that are both in class and course, students that are in class and not in course, and students that are in course and not in class. Filter your results where either class_id or course_id is null then to get the students missing in course or class. At last group by id and list the students.
select coalesce(class.class_id, course.course_id) as id
, listagg(class.stud_name, ',') within group (order by class.stud_name) as missing_in_course
, listagg(course.stud_name, ',') within group (order by course.stud_name) as missing_in_class
from class
full outer join course
on (class.class_id = course.course_id and class.stud_name = course.stud_name)
where class.class_id is null or course.course_id is null
group by coalesce(class.class_id, course.course_id);
Here is the SQL fiddle showing how it works: http://sqlfiddle.com/#!4/8aaaa/2
EDIT: In Oracle 9i there is no listagg. You can use the inofficial function wm_concat instead:
select coalesce(class.class_id, course.course_id) as id
, wm_concat(class.stud_name) as missing_in_course
, wm_concat(course.stud_name) as missing_in_class
from class
full outer join course
on (class.class_id = course.course_id and class.stud_name = course.stud_name)
where class.class_id is null or course.course_id is null
group by coalesce(class.class_id, course.course_id);
In a table that stores multiple rows per employee, I want to pull one row per employee that represents the most recent entry for each employee. Here's where I am with hand-written SQL:
SELECT [all the selected columns here]
FROM Nominations t
inner join
(select max(NominationId) mostRecentNominationId,
EmployeeId from Nominations group by EmployeeId) n
on n.mostRecentNominationId = t_.NominationId
From source data like this:
nomination_id employee_id
-------------------------------
1 5
2 5
4 10
7 10
That'll give me something like this:
nomination_id employee_id
-------------------------------
2 5
7 10
I haven't been able to figure out how to accomplish that type of query via NHibernate ICriteria. Any thoughts?
Here is what you need to do:
DetachedCriteria dCriteria = DetachedCriteria.For<Nomination>("nomination")
.SetProjection(Projections.Max("nomination.Id"))
.Add(Restrictions.EqProperty("nomination.EmployeeId", "employee.Id"));
var nominations = Session.CreateCriteria<Nomination>("nom")
.CreateCriteria("Employee", "employee")
.Add(Subqueries.PropertyEq("nom.Id", dCriteria)).List<Nomination>();
This is not equilevant to the SQL query providfed in the question but it does exactly the same thing.
The SQL query that is generated by the above criteria query is:
SELECT *
FROM Nomination nom
inner join Employee employee on nom.EmployeeId=employee.EmployeeId
WHERE nom.NominationId =
(SELECT max(nomination.NominationId) as maxID
FROM Nomination nomination
WHERE nomination.EmployeeId = employee.EmployeeId)