I may be asking too much but I want to do a left outer join between two cores
and get data from A only where B does not have related data.
Following is exactly my equivalent SQL query (for simplicity I have removed other conditions),
1. SELECT A.* FROM A AS A
WHERE A.ID NOT IN (SELECT B.A_ID FROM B AS B WHERE B.STATUS_ID != 1)
I understand that solr join is actually subquery, I need data from only A.
It would be very easy if the not was not there in where condition for sub query.
For example,
2. SELECT A.* FROM A AS A
WHERE A.ID IN (SELECT B.A_ID FROM B AS B WHERE B.STATUS_ID != 1)
I can have q={!join from=aId to=id fromIndex=b}(-statusId:1).
How can I do a nagete here, i.e. solr query for 1
Related
We are aware of how map join and SMBM join works reducing the execution time( eliminating reduce phase i.e eliminating shuffle).
Ex: For join between two tables
select a.col1,b.col2 from
a join b on a.col1=b.col1
(both the tables are bucketed on col1 into same no of buckets)
But while joining with 3 or more tables on different columns,
Ex:
Select a. col1,b.col3,c.col2,d.date from
a join b on a.id=b.id join c on a.state=b.state join d on c.date=d.date
A scenario like this, how bucketing will help, if we don't want to split up the query in multiple smaller queries.
When joining multiple tables, involving all join types (inner, left,cross, full etc), is there any specific order in which joins are evaluated, like we have BODMAS in Mathematics or it always reads from left to right in the order we specified.
I don't have the exact SQL but here is a sample SQL:
Select * from
A,
B
LEFT JOIN
C
ON B.ID = C.ID,
D
FULL JOIN
E
ON
D.ID = E.ID;
Will it be like A cross joining with B and the result Left joining with C and so on..?
OR
A cross joining with the Left join of B and C..
Newbie with SQL development. I got this strange scenario where I want to join 3 tables Table A,B,C. The use case is to return column X which is a primary key in table C. The column X is also a FK in table A and B.
Now I want to create a view by left joining all the 3 tables. The view has have 4 columns, A.id, B.id, C.A_X, C.B_X
The users can either use A.id or B.id to get the data. Now that's the scenario.
How should I join these tables so that I don't miss any values for C.X for every A.id and B.id.
Sample results:
A.id B.id C.A_X C.B_X
1 null ABC null
null 2 null XYZ
Cheers!!
What is the ANSI-92 equivalent of the following old Informix SQL query?
select *
from categories c,
orders o,
outer (employees e, person p)
where c.categoryid = o.categoryid
and p.personid = e.id
and o.employeeid = e.id
and o.orderid = 7742
and e.term_date is NULL
I cannot seem to figure out exactly what the "outer (table1, table2)" syntax means.
Mike Burdick's answer is, I believe, essentially correct — but I'm not completely sure of that. I'd be a little more comfortable with the comparison if the query were written as:
SELECT *
FROM Categories AS C
JOIN Orders AS O ON C.CategoryID = O.CategoryID
LEFT JOIN
(SELECT * FROM
FROM Employees AS E
JOIN Person AS P ON E.ID = P.PersonID
) AS E ON O.EmployeeID = E.ID
WHERE O.OrderID = 7742
AND E.Term_Data IS NULL
The OUTER (Employees e, Person p) in the original query is an inner-join sub-query that is outer-joined to the main query, which I've made clearer in my version by using the sub-query, but I think Mike's version is OK too. My concern is that Mike's version might more nearly equivalent to this (where the parentheses around employees e are optional in this scenario):
select *
from categories c,
orders o,
outer (employees e),
person p
where c.categoryid = o.categoryid
and p.personid = e.id
and o.employeeid = e.id
and o.orderid = 7742
and e.term_date is NULL
I'd need to think hard before coming up with data sets that could distinguish between the two queries (either the original query in the question and the slight rewrite above, or between Mike's answer and mine).
One other nagging doubt is that Informix's old-style non-standard OUTER join notation has a quirk that the standard notation simply does not support. The problem can occur when filtering on data in the subordinate table (RHS of a left outer join). The rows in the dominant table (in this case, tables — orders and categories) are preserved by Informix even when there was a match in the subordinate table that got filtered out. I think that it works OK this time because the filter condition that I'm concerned about, which is AND e.term_date IS NULL, uses IS NULL. You could run into the problem if the filter condition was AND e.term_date > MDY(7,4,2032) (and there was a row in employees that did not match the filter condition), but I think IS NULL is OK. The Informix behaviour is hard to explain, and hard to justify beyond "that is the way it works and it was documented to work thus in 1987±2 years, and backwards compatibility deals with the rest". It is only the Informix-only OUTER join notation that behaves weirdly. The ANSI-standard LEFT OUTER JOIN notation works according to the standard. But it does make conversion a challenge if this quirk affects your legacy code.
TL;DR Test the query results very carefully.
Something like:
select *
from categories c
Join orders o
on c.categoryid = o.categoryid
Left Join employees e
on o.employeeid = e.id
Join person p
on e.id = p.personid
where o.orderid = 7742
and e.term_data is null
I have 3 oracle tables. A joins to B and B joins to C. I want all records from A irerspective of whether a corresponding record exists in B or C. I wrote a query like this:
select a.name from a,b,c where a.a_id = b.b_id(+) and b.b_id = c.c_id(+)
This query does not seem right to me, particularly with the second join. What will exactly happen if there is a record in A but correspondingly nothing in B and C? Will it still fetch the record?
For some reason the above query returns same count of records as select a.name from a
So I am guessing that the query is right? Also is there a better way to rewrite the query?
I presume the better query can be
Select a.name from A a left join B b on a.a_id=b.b_id inner join C c on b.b_id=c.c_id
This should give the result as you have expected
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