I have 3 different CTEs(a,b,c) which have columns date, id, and value. Only the value column has different values in it. Date and Id will have the same values in it.
select a.date,a.id,a.value,b.date,b.id,b.value,c.date,c.id,c.value
from table_a a
full outer join table_b on b.id = a.id
full outer join table_c on c.id = b.id
The above code gave the following outputenter image description here
I want the following output, where the date column is merged and acts as an index
enter image description here
how do I get the output in the second picture.
Use coalesce, typicall when your work with full join
select
coalesce(a.date, b.date, c.date) as ddate,
a.id,a.value,
b.id,b.value,
c.id,c.value
from table_a a
full outer join table_b on b.id = a.id
full outer join table_c on c.id = b.id
Related
Assume there are three total tables A,B, and C
Each table contains following attributes:
Table A: "date", "id", "tv_sales_amt"
Table B: "date", "id", "newspaper_sales_amt"
Table C: "date", "id", "radio_sales_amt"
Using join operators, I'm trying to achieve a single table view with:
Result table:
"date", "id", "tv_sales_amt", "newspaper_sales_amt", "radio_sales_amt"
Desired look of the result table:
date id tv_sales_amt newspaper_sales_amt radio_sales_amt
--------------------------------------------------------------------
20190101 012C 2000 1850 NULL
20190102 102D 1000 NULL 1300
.
.
.
Here are some queries that I've tried:
Query #1:
SELECT
A.date, A.id, tv_sales_amt, newspaper_sales_amt, radio_sales_amt
FROM A
INNER JOIN B ON A.id = B.id
INNER JOIN C ON A.id = C.id
Using inner inner-join, I get duplicated values, which is understandable but is not what I'm looking for.
Query #2:
SELECT
A.date, A.id, tv_sales_amt, newspaper_sales_amt, radio_sales_amt
FROM A
FULL OUTER JOIN B ON A.id = B.id
FULL OUTER JOIN C ON A.id = C.id
Since inner-join would only return results from Table B and C (newspaper_sales_amt and radio_sales_amt) that intersects with Table A, I tried full-outer-join in the hopes that it would give me overview of entire results, even though it includes null values.
With both options that I've tried, I wasn't able to get the expected result (Desired look described above).
Would someone be able to tell me what I'm doing wrong here?
I'm using the latest version of SQL Server Management Studio.
I do know that there must be lots of null values if I were to take an overview of tv_sales_amt, newspapers_sales_amt, and radio_sales_amt, but currently, there are no null values but with duplicates.
Your description implies that date also should be the part of joins.
select coalesce(a.date, b.date, c.date) [date],
coalesce(a.id, b.id, c.id) id,
a.tv_sales_amt, b.newspaper_sales_amt, c.radio_sales_amt
from tableA a
full join tableB b on a.id = b.id and a.date = b.date
full join tableC c on (c.id = b.id and c.date = b.date) or
(c.id = a.id and c.date = a.date);
EDIT: This is DbFiddle demo. Try removing coalesce() for date or id (removing in only one of them helps to see it better).
EDIT: Maybe this shows the need for coalesce() better:
select coalesce(a.date, b.date, c.date) [date],
a.id idA, b.id idB, c.id idC,
a.tv_sales_amt, b.newspaper_sales_amt, c.radio_sales_amt
from tableA a
full join tableB b on a.id = b.id and a.date = b.date
full join tableC c on (c.id = b.id and c.date = b.date) or
(c.id = a.id and c.date = a.date);
Full outer joins are tricky. I would suggest:
SELECT COALESCE(A.DATE, B.DATE, C.DATE) as date,
COALESCE(A.ID, B.ID, C.ID) as id,
A.tv_sales_amt, B.newspaper_sales_amt, C.radio_sales_amt
FROM A FULL JOIN
B
ON B.id = A.id AND
B.date = A.date FULL JOIN
C
ON C.id = COALESCE(A.id, B.id) AND
C.date = COALESCE(B.date, B.date);
I find that using COALESCE() in the ON clause simplifies adding more conditions. From a performance perspective, both COALESCE() and OR are pretty bad.
Here there are two tables. Table A and Table B I tried joining these two tables using the outer join to get all of the rows which is the resultant_table from both tables and it isn't working for some reason the screenshot at the end shows the error that I'm getting when I happen to run the query. I wanted the output as showed in the resultant table.
Here is the script that i used,
SELECT table_b.date,
table_b.student,
table_b.location,
table_b.sub_division,
table_a.part_time_pay,
table_b.days_worked
FROM table_a
FULL OUTER JOIN table_b
ON table_a.date = table_b.date
AND table_a.student = table_b.student;
It is doing exactly what you specify. Use coalesce() to combine values from the two tables:
SELECT COALESCE(a.date, b.date) as date,
COALESCE(a.student, b.student) as student,
b.location, b.sub_division,
a.part_time_pay, b.days_worked
FROM table_a a FULL JOIN
table_b b
ON a.date = b.date AND
a.student = b.student;
I'm not sure how you want to handle LOCATION, and SUBDIVISION. What if they have different values? I might think you want to put them in the JOIN conditions and then:
SELECT COALESCE(a.date, b.date) as date,
COALESCE(a.student, b.student) as student,
COALESCE(a.location, b.location) as location,
COALESCE(a.sub_division, b.sub_division) as sub_division,
a.part_time_pay, b.days_worked
FROM table_a a FULL JOIN
table_b b
ON a.date = b.date AND
a.student = b.student AND
a.location = b.location AND
a.sub_division = b.sub_division;
Here is the Exercise we were given to practice our SQL refresher
Get all rows from TableA. If a match is available in both TableB and TableC, include it. This means that if data is available in TableB or TableC, but not both, data from both willbe excluded and only TableA data will be show
This is currently my full syntax I am using at the current moment.
SELECT *
FROM dbo.TableA a
LEFT JOIN dbo.TableB b ON a.ID = b.ID
LEFT JOIN dbo.TableC c ON a.ID = b.ID AND b.ID = c.ID
WHERE a.ID <100;
go
And this is the corresponding output I am getting.
I am trying to change Column B record 2 into NULL as it does not match Column C. Is there anyway I can get something like this to work, if I try this in the syntax it throws an identifier can not be found.
LEFT JOIN dbo.TableB b
on a.ID = b.ID and TableC.ID = b.ID
Expecting
All From Table A
Rows from TableB that match TableA and TableC
Rows from TableC that match TableA and TableB
Figured out my logic was a bit wrong.
I decided to try and layout the tables differently to see if that works and it ended up getting to what I needed
select *
from dbo.TableB b
inner join dbo.TableC c
on b.ID = c.ID
right outer join dbo.TableA a
on b.ID = a.ID
where a.ID < 100;
go
I have two tables Table A and Table B
Table A
1. *id*
2. *name*
Table B
1. *A.id*
2. *datetime*
I want to select
1. *A.id*
2. *A.name*
3. *B.datetime*
Even if table B do not contains a row with A.id for specific day and it should replace that column with NULL
e.g
Table A contains
1. *(1 , Haris)*
2. *(2, Hashsim)*
Table B Contains following for today's date.
1. *(1, '2014-12-26 08:00:00')*
I should show 2 results with id 1 and 2 instead of only id 1.
Using LEFT OUTER JOIN with WHERE Clause makes it a LEFT INNER JOIN, how to work around that ?
SELECT A.id, A.name, b.datetime
FROM A
LEFT Outer JOIN B on B.id = A.id
Use LEFT OUTER JOIN to get all the rows from Left table and one that does not have match will have NULL values in Right table columns
SELECT A.id,
A.name,
B.[datetime]
FROM tableA A
LEFT OUTER JOIN tableB B
ON A.Id = B.id
AND B.[datetime] < #date
SELECT a.id, a.name, b.datetime
FROM A
LEFT JOIN B on B.aid = a.id
WHERE coalesce(B.datetie, '1900-01-01') < #MyDateTime
Select A.id,A.name,B.datetime
from tableA A
Left join
(
SELECT B.ID,B.datetime
FROM tableB B
WHERE B.datetime <= 'myDateTime'
)B
ON A.aid = B.id
Say I have three tables in SQL server 2008 R2
SELECT a.*, b.*, c.*
FROM
Table_A a
RIGHT JOIN Table_B b ON a.id = b.id
LEFT JOIN Table_C c ON b.id = c.id
or
SELECT a.*, b.*, c.*
FROM
Table_A a
RIGHT JOIN Table_B b ON a.id = b.id
JOIN Table_C c ON b.id = c.id
also, does it matter if I use b.id or a.id on joining c?
i.e. instead of JOIN Table_C c ON b.id = c.id, use JOIN Table_C c ON a.id = c.id
Thank you!
If it doesn't change the semantics of the query, the database server can reorder the joins to run in whichever way it thinks is more efficient.
Usually, if you want to force a certain order, you can use inline view subqueries, as in
SELECT a.*, x.*
FROM
Table_A a
RIGHT JOIN
(
SELECT *, b.id as id2 FROM Table_B b
LEFT JOIN Table_C c ON b.id = c.id
) x
ON a.id = x.id2
According to the definitions:
JOIN
: Return rows when there is at least one match in both tables
LEFT JOIN Return all rows from the left table, even if there are no matches in the right table
RIGHT JOIN Return all rows from the right table, even if there are no matches in the left table
The first option would include all raws from the 1st Join on Tables a and b even if there are no matching ones in table c, while the second statement would show only raws which match ones in table c.
regarding the second question i guess it would make a difference, since the 1st join includes all ids from table b, even though there are no matching ones in table a, so once you change your Join creterium to a.id you will get a different set of ids than b.id.
Yes, you do need a LEFT JOIN after a RIGHT JOIN
See
http://sqlfiddle.com/#!3/2c079/5/0
http://sqlfiddle.com/#!3/2c079/6/0
If you don't, the (inner) JOIN at the end will cancel out the effect of your RIGHT JOIN.
That wouldn't make any sense to have a RIGHT JOIN if you don't care. And if you care, you will have to add a LEFT JOIN after it.