I currently want to combine two SQL queries into one. This is a bit similar to SQL: Taking the result of of query and using it another - combine . Suppose there are two queries:
SQL Statement
1.) SELECT *
FROM (SELECT B.example1
FROM EXAMPLE1A A
INNER JOIN EXAMPLE1B B ON A.ID = B.ID
WHERE A.ABC ='ABC'
ORDER BY A.ORDER_BY ) as colstate
2.) SELECT colstate
FROM EXAMPLE_TABLE
WHERE EFG LIKE '%'
AND BGTHAN >= '1'
AND SMTHAN <= '100'
ORDER BY ORDER_BY ASC
I want to use the result in query 1.) as the colstate (column statement) in query 2.). But:
What Have I tried is:
SELECT (SELECT B.example1
FROM EXAMPLE1A A
INNER JOIN EXAMPLE1B B
ON A.ID = B.ID
WHERE A.ABC ='ABC'
ORDER BY A.ORDER_BY )
FROM EXAMPLE_TABLE
WHERE EFG LIKE '%'
AND BGTHAN >= '1'
AND SMTHAN <= '100'
ORDER BY ORDER_BY ASC
And it turns out to be Error: Scalar subquery is only allowed to return a single row , how should I replace the "=" into "IN"? Or is my statement totally wrong?
The error says that query you are using as column statement must return at most a single row.
It should probably look something like this:
SELECT (SELECT B.example1
FROM EXAMPLE1A A
INNER JOIN EXAMPLE1B B
ON A.ID = B.ID
WHERE A.ABC ='ABC'
AND A.SOME_COLUMN = E.SOMECOLUMN // retrieve only relevant data for this row
ORDER BY A.ORDER_BY )
FROM EXAMPLE_TABLE E
WHERE EFG LIKE '%'
AND BGTHAN >= '1'
AND SMTHAN <= '100'
ORDER BY ORDER_BY ASC
"Combine two queries into one" - that's not a good specs. Try to find out what exactly you want to get as a FLAT 2-dimensional table, think of nested SELECTs as of nested loops where the inner one can only set a single value for parent's row. Like this:
[Outer loop - parent row]
[Inner loop - children rows]
// all you can do here is change a single parent's field to anything
// like constant/sum/avg/topmost/ugly-subquery-returning-a-single-result
[/Inner loop]
[/Outer loop]
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