I want to sum two tables. Both tables contain the number of rowas grouped by a category:
number category
5 A
4819 B
1 C
number category
12043 B
I tried the following:
select a.category, a.number + b.number as number
from a
right join b
on a.category = b.category
I get:
number category
4 16862
I don't understand why I don't get all three categories. I trief left join instead of right join.
The problem with you right join is that a table should appear on the right side of the join. Or, using a left join, we could write:
SELECT
a.category,
a.number + COALESCE(b.number, 0) AS number
FROM tablea a
LEFT JOIN tableb b
ON a.category = b.category;
But this answer assumes that the a table would contain every category which you want to appear in your result set. For a more general solution, we might have to use a full outer join:
SELECT
COALESCE(a.category, b.category) AS category,
COALESCE(a.number, 0) + COALESCE(b.number, 0) AS number
FROM tablea a
FULL OUTER JOIN tableb b
ON a.category = b.category;
You can use union all and aggregation:
select category ,sum(number) value
from (
select category, number from tablea
union all select category, number from tableb
)
group by category
Another option is to do a full outer join: this would allow values coming from both sides of the join:
select
coalesce(ta.category, tb.category) number,
sum(coalesce(ta.number, 0) + coalesce(tb.number, 0)) value
from tablea ta
full outer join tableb tb on ta.category = tb.category
group by coalesce(ta.category , tb.category )
I should have used nvl(). This works:
select a.category, nvl(a.number, 0) + nvl(b.number, 0) as number
from a
right join b
on a.category = b.category
Related
I have two sets A and B. I want to display counts of A as well as counts on A (intersection) B using condition X.
Code I am using
SELECT COUNT(A) as total, COUNT(IF (condition_X)) as chg
FROM A
FULL OUTER JOIN B
ON JOIN KEY Y
I am able to get the intersection but not the count of A in total.
Perhaps you just want a cross join?
select *
from (select count(*) as cnt_a from a) a cross join
(select count(*) as cnt_b
from a join
b
on y
where condition
) b
Simply left join the two
Select count(A.id=B.id),
count(A.id)
from A left join B on A.id=B.id
where condition='x'
Here is pseudocode of what I am trying to achieve
Select * from TableA
if(TableA.criteria != 1)
inner join TableB.criteria = TableA.criteria
I must do it in view can use sp, functions, etc.
Thanks for any help you will be able to provide
Is this what you want?
Select a.*, b.* from TableA a join TableB b
on b.criteria = case when a.Criteria = 1
then 1 else null end
This may be what you want:
select a.*, b.*
from a left join
b
on b.criteria = a.criteria and b.criteria = 1;
The left join will keep all rows in a, even when the on condition is not true. The extra columns from b will be NULL, unless the criterias are both "1".
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
I have two tables
Table A
-------
ID
ProductName
Table B
-------
ID
ProductID
Size
I want to join these two tables
SELECT * FROM
(SELECT * FROM A)
LEFT JOIN
(SELECT * FROM B)
ON A.ID = B.ProductID
This is easy, I will get all rows from A multiplied by rows matched in B, and NULL fields if there is no match.
But here comes the tricky question, how can I get all rows from A with NULL fields for table B, even if there is a match, so I get an extra line with NULL values plus all the matches?
SELECT A.*
, B3.ID
, B3.ProductID
, B3.Size
FROM A
LEFT JOIN
(
SELECT ProductID as MatchID
, ID
, ProductID
, Size
FROM B
UNION ALL
SELECT ID
, null
, null
, null
FROM A A2
) B3
ON A.ID = B3.MatchID
Live example at SQL Fiddle.
Instead of using UNION ALL in a subquery as suggested by others, you could also (and I would) use UNION ALL at the outer level, which keeps the query simpler:
SELECT A.ID, A.ProductName, B.ID, B.Size
FROM A
INNER JOIN B
ON B.ProductID = A.ID
UNION ALL
SELECT A.ID, A.ProductName, NULL, NULL
FROM A
Since every join is going to be successful, we can switch to a full/inner join:
SELECT
*
FROM
A
INNER JOIN
(SELECT ID,ProductID,Size FROM B
UNION ALL
SELECT NULL,ID,NULL FROM A) B
ON
A.ID = B.ProductID
Now would be a very good time to switch to naming columns explicitly, rather than using SELECT *
Or, if, as per #Andomar's comment, you need all of the B columns to be NULL:
SELECT
A.ID,A.ProductName,
B.ID,B.ProductID,B.Size
FROM
A
INNER JOIN
(SELECT ID,ProductID,Size,ProductID as MatchID FROM B
UNION ALL
SELECT NULL,NULL,NULL,ID FROM A) B
ON
A.ID = B.MatchID
I need to simulate the left join effect without using the "left join" key.
I have two tables, A and B, both with id and name columns. I would like to select all the dbids on both tables, where the name in A equals the name in B.
I use this to make a synchronization, so at the beginning B is empty (so I will have couples with id from A with a value and id from B is null). Later I will have a mix of couples with value - value and value - null.
Normally it would be:
SELECT A.id, B.id
FROM A left join B
ON A.name = B.name
The problem is that I can't use the left join and wanted to know if/how it is possible to do the same thing.
you can use this approach, but you must be sure that the inner select only returns one row.
SELECT A.id,
(select B.id from B where A.name = B.name) as B_ID
FROM A
Just reverse the tables and use a right join instead.
SELECT A.id,
B.id
FROM B
RIGHT JOIN A
ON A.name = B.name
I'm not familiar with java/jpa. Using pure SQL, here's one approach:
SELECT A.id AS A_id, B.id AS B_id
FROM A INNER JOIN B
ON A.name = B.name
UNION
SELECT id AS A_id, NULL AS B_id
FROM A
WHERE name NOT IN ( SELECT name FROM B );
In SQL Server, for example, You can use the *= operator to make a left join:
select A.id, B.id
from A, B
where A.name *= B.name
Other databases might have a slightly different syntax, if such an operator exists at all.
This is the old syntax, used before the join keyword was introduced. You should of course use the join keyword instead if possible. The old syntax might not even work in newer versions of the database.
I can only think of two ways that haven't been given so far. My last three ideas have already been given (boohoo) but I put them here for posterity. I DID think of them without cheating. :-p
Calculate whether B has a match, then provide an extra UNIONed row for the B set to supply the NULL when there is no match.
SELECT A.Id, A.Something, B.Id, B.Whatever, B.SomethingElse
FROM
(
SELECT
A.*,
CASE
WHEN EXISTS (SELECT * FROM B WHERE A.Id = B.Id) THEN 1
ELSE 0
END Which
FROM A
) A
INNER JOIN (
SELECT 1 Which, B.* FROM B
UNION ALL SELECT 0, B* FROM B WHERE 1 = 0
) B ON A.Which = B.Which
AND (
A.Which = 0
OR (
A.Which = 1
AND A.Id = b.Id
)
)
A slightly different take on that same query:
SELECT A.Id, B.Id
FROM
(
SELECT
A.*,
CASE
WHEN EXISTS (SELECT * FROM B WHERE A.Id = B.Id) THEN A.Id
ELSE -1 // a value that does not exist in B
END PseudoId
FROM A
) A
INNER JOIN (
SELECT B.Id PseudoId, B.Id FROM B
UNION ALL SELECT -1, NULL
) B ON A.Which = B.Which
AND A.PseudoId = B.PseudoId
Only for SQL Server specifically. I know, it's really a left join, but it doesn't SAY LEFT in there!
SELECT A.Id, B.Id
FROM
A
OUTER APPLY (
SELECT *
FROM B
WHERE A.Id = B.Id
) B
Get the inner join then UNION the outer join:
SELECT A.Id, B.Id
FROM
A
INNER JOIN B ON A.name = B.name
UNION ALL
SELECT A.Id, NULL
FROM A
WHERE NOT EXISTS (
SELECT *
FROM B
WHERE A.Id = B.Id
)
Use RIGHT JOIN. That's not a LEFT JOIN!
SELECT A.Id, B.Id
FROM
B
RIGHT JOIN A ON B.name = A.name
Just select the B value in a subquery expression (let's hope there's only one B per A). Multiple columns from B can be their own expressions (YUCKO!):
SELECT A.Id, (SELECT TOP 1 B.Id FROM B WHERE A.Id = B.Id) Bid
FROM A
Anyone using Oracle may need some FROM DUAL clauses in any SELECTs that have no FROM.
You could use subqueries, something like:
select a.id
, nvl((select b.id from b where b.name = a.name), "") as bId
from a
you can use oracle + operator for left join :-
SELECT A.id, B.id
FROM A , B
ON A.name = B.name (+)
Find link :-
Oracle "(+)" Operator
SELECT A.id, B.id
FROM A full outer join B
ON A.name = B.name
where A.name is not null
I'm not sure if you just can't use a LEFT JOIN or if you're restricted from using any JOINS at all. But as far as I understand your requirements, an INNER JOIN should work:
SELECT A.id, B.id
FROM A
INNER JOIN B ON A.name = B.name
Simulating left join using pure simple sql:
SELECT A.name
FROM A
where (select count(B.name) from B where A.id = B.id)<1;
In left join there are no lines in B referring A so 0 names in B will refer to the lines in A that dont have a match
+ or A.id = B.id in where clause to simulate the inner join