It would appear you have data you are not expecting..The part of your code that has WHERE rn = 1, must be bringing back more than 1 row.  There doesn't...

Here's my attempt in one pass:
CREATE TABLE #Transactions (
    Date1 date NOT NULL PRIMARY KEY CLUSTERED,
    Amount1 int,
    Amount2 int
);
INSERT INTO #Transactions (Date1, Amount1, Amount2)
    VALUES    ('20180101', 1000000,...

Honestly, a cursor within a cursor, that effectively needs to be dynamic, just seems a tad much to me...   Too difficult to create easily, and overly complex to troubleshoot.  Pretty...

One way would be to change your table design to use just one table called Tags, and have a column that indicates TagType (Custom or Stock - perhaps simply C...

Be careful about changing functionality somewhere deep in a nest of such daisy-chained stored procedures.   Once you have a nest like that, you may find you don't know that any...

I would tend to lean toward establishing ALL the linkages between the databases as a single final step done by an "incremental" T-SQL script, and let the base objects get...

In terms of PIVOT, if you are using the actual PIVOT keyword as part of your query, that CAN be trouble, especially with a large number of resulting columns.   It's...

Depends rather heavily on table size and the number of rows to be handled, along with whether or not there are appropriate indexes to handle the queries, along with the...