Why doesn't this SQL sub query statement work? - sql

Question

The statement produces the following error.
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.
I presume I somehow need to concatenate the field names in the subquery?
SELECT (
SELECT COALESCE(Table_Field, Field) AS Fields
FROM API_Objects_Fields
WHERE Field IN (
'fullname'
,'confirmed'
,'primary_email'
,'location_short'
)
)
FROM user_basics U
INNER JOIN Pod_Membership PM ON U.UserID = PM.UserID
WHERE PM.PodID = 164
ORDER BY U.Ctime DESC
The sub query specifies the fields to be returned from the table.

Answer 1

DECLARE #Name VARCHAR(1000)
Select #Name =
COALESCE(#Name,'') +Table_Field + ';'
FROM API_Objects_Fields
WHERE Field IN
( 'fullname' ,'confirmed' ,'primary_email' ,'location_short' )
Select #Name As FieldName
#akfkmupiwu need to do like this for above comment

Answer 2

WITH CTE AS
(SELECT (
SELECT DISTINCT TOP 1 COALESCE(Table_Field, Field)
FROM API_Objects_Fields F
WHERE F.UserID = PM.UserID AND F.Field IN (
'fullname'
,'confirmed'
,'primary_email'
,'location_short'
)
)AS Fields,
ROW_NUMBER()OVER (PARTITION BY Table_Field ORDER BY FIELD)AS RN
FROM user_basics U
INNER JOIN Pod_Membership PM ON U.UserID = PM.UserID
WHERE PM.PodID = 164
ORDER BY U.Ctime DESC
)
Select * from CTE WHERE RN = 1
It is an assumption query basing on your question

Answer 3

What the error is telling you
The problem with your query is exactly what the error says, it brings back more than one result. Since your subquery is in the select portion of the outer query (as opposed to the from or the where), sql is looking for the one value to populate the specific column. Think of it more in terms of filling in an excel spreadsheet. You cannot add two separate values to one cell. Instead, you need the data to go into two separate rows.
On another note, coalesce checks if the first value is null, if it is then it returns the second value. If the first value is not null, that value is returned. It sounds to me that this is not the behavior that you are looking for.
How to fix this
You need to either change your query to pull back different rows for each of the possible values that Fields can be or you need to find a way to specify only one value to return for Fields. Since I am unsure what you are looking for, I am going to demonstrate the first way of solving this.
Data
Your question does not provide any data for API_Objects_Fields, so I am going to make some up. Let's assume the columns in this table are Field_ID, Table_Field, and Field and let's say that your table looks like this:
Field_ID | Table_Field | Field
1 | Alan Turing | fullname
2 | Catherine Zeta Jones | fullname
3 | True | confirmed
4 | MN | location_short
5 | 123-456-7890 | phone_number
As I mentioned before, right now your query would try to pull back the rows where the field is fullname, confirmed, or location_short all. Instead of trying to stuff one column of one row. full of 4 results, let's change your query to bring back 4 rows
The Query
SELECT f.Table_Field, Field
FROM user_basics U
INNER JOIN Pod_Membership PM ON U.UserID = PM.UserID
INNER JOIN (
SELECT Table_Field, Field
FROM API_Objects_Fields
WHERE Field IN (
'fullname'
,'confirmed'
,'primary_email'
,'location_short'
)
) f
WHERE PM.PodID = 164
ORDER BY U.Ctime DESC
What will happen
This query will now pull back data that looks more like this:
Table_Field | Fields
Alan Turing | fullname
Catherine Zeta Jones | fullname
True | confirmed
MN | location_short
However, I think you will be surprised with the results you actually end up with. Since the query does not connect the data in API_Objects_Fields with any other tables, you would get the values from the results table above over and over again. In fact, you would get the values above for every single row returned by
Select *
From user_basics u
INNER JOIN Pod_Membership PM ON U.UserID = PM.UserID
WHERE PM.PodID = 164
If this query returns 12 results, you would end up with 12 Alan Turings, 12 Catherine Zeta Jones, 12 Trues, and 12 MNs. If this is not the result you are looking for, you will need to add an ON portion to the inner join so the results from f are connected with the other tables.