Join on resultant table of another join without using subquery,CTE or temp tables - sql

Question

My question is can we join a table A to resultant table of inner join of table A and B without using subquery, CTE or temp tables ?
I am using SQL Server.
I will explain the situation with an example
The are two tables GoaLScorers and GoalScoredDetails.
GoaLScorers
gid Name
-----------
1 A
2 B
3 A
GoalScoredDetails
DetailId gid stadium goals Cards
---------------------------------------------
1 1 X 2 1
2 2 Y 5 2
3 3 Y 2 1
The result I am expecting is if I select a stadium 'X' (or 'Y')
I should get name of all who may or may not have scored there, also aggregate total number of goals,total cards.
Null value is acceptable for names if no goals or no cards.
I can get the result I am expecting with the below query
SELECT
gs.name,
SUM(goal) as TotalGoals,
SUM(cards) as TotalCards
FROM
(SELECT
gid, stadium, goal, cards
FROM
GoalScoredDetails
WHERE
stadium = 'Y') AS vtable
RIGHT OUTER JOIN
GoalScorers AS gs ON vtable.gid = gs.gid
GROUP BY
gs.name
My question is can we get the above result without using a subquery or CTE or temp table ?
Basically what we need to do is OUTER JOIN GoalScorers to resultant virtual table of INNER JOIN OF GoalScorers and GoalScoredDetails.
But I am always faced with ambiguous column name error as "gid" column is present in GoalScorers and also in resultant table. Error persists even if I try to use alias for column names.
I have created a sql fiddle for this her: http://sqlfiddle.com/#!3/40162/8

Answer 1

SELECT gs.name, SUM(gsd.goal) AS totalGoals, SUM(gsd.cards) AS totalCards
FROM GoalScorers gs
LEFT JOIN GoalScoredDetails gsd ON gsd.gid = gs.gid AND
gsd.Stadium = 'Y'
GROUP BY gs.name;
IOW, you could push your where criteria onto joining expression.

Answer 2

The error Ambiguous column name 'ColumnName' occurs when SQL Server encounters two or more columns with the same and it hasn't been told which to use. You can avoid the error by prefixing your column names with either the full table name, or an alias if provided. For the examples below use the following data:
Sample Data
DECLARE #GoalScorers TABLE
(
gid INT,
Name VARCHAR(1)
)
;
DECLARE #GoalScoredDetails TABLE
(
DetailId INT,
gid INT,
stadium VARCHAR(1),
goals INT,
Cards INT
)
;
INSERT INTO #GoalScorers
(
gid,
Name
)
VALUES
(1, 'A'),
(2, 'B'),
(3, 'A')
;
INSERT INTO #GoalScoredDetails
(
DetailId,
gid,
stadium,
goals,
Cards
)
VALUES
(1, 1, 'x', 2, 1),
(2, 2, 'y', 5, 2),
(3, 3, 'y', 2, 1)
;
In this first example we recieve the error. Why? Because there is more than one column called gid it cannot tell which to use.
Failed Example
SELECT
gid
FROM
#GoalScoredDetails AS gsd
RIGHT OUTER JOIN #GoalScorers as gs ON gs.gid = gsd.gid
;
This example works because we explicitly tell SQL which gid to return:
Working Example
SELECT
gs.gid
FROM
#GoalScoredDetails AS gsd
RIGHT OUTER JOIN #GoalScorers as gs ON gs.gid = gsd.gid
;
You can, of course, return both:
Example
SELECT
gs.gid,
gsd.gid
FROM
#GoalScoredDetails AS gsd
RIGHT OUTER JOIN #GoalScorers as gs ON gs.gid = gsd.gid
;
In multi table queries I would always recommend prefixing every column name with a table/alias name. This makes the query easier to follow, and reduces the likelihood of this sort of error.