Error Incorrect syntax near the keyword 'SELECT' - sql

Question

I need help.
I write this query
SELECT SUM(fi.etiliquido) FROM fi WHERE fi.fno IN (
SELECT * from divideString(
SELECT TOP 1 REPLACE(CAST( u.nrdoc AS nvarchar),'/',',') FROM u_ups1 as u WHERE 1057 IN (
SELECT * FROM divideString(REPLACE(CAST(u.nrdoc AS nvarchar),'/',','))
)
)
)
but sql server return this error
Msg 156, Level 15, State 1, Line 4 Incorrect syntax near the keyword
'SELECT'. Msg 102, Level 15, State 1, Line 7 Incorrect syntax near
')'.
and I don't know why.
Can you help me?
UPDATE
divideString is a function get a string and returns the numbers in that string
CREATE FUNCTION divideString (#InStr VARCHAR(MAX))
RETURNS #TempTab TABLE
(id int not null)
AS
BEGIN
SET #InStr = REPLACE(#InStr + ',', ',,', ',')
DECLARE #SP INT
DECLARE #VALUE VARCHAR(1000)
WHILE PATINDEX('%,%', #INSTR ) <> 0
BEGIN
SELECT #SP = PATINDEX('%,%',#INSTR)
SELECT #VALUE = LEFT(#INSTR , #SP - 1)
SELECT #INSTR = STUFF(#INSTR, 1, #SP, '')
INSERT INTO #TempTab(id) VALUES (#VALUE)
END
RETURN
END

Answer 1

You need parentheses around subqueries (except for in subqueries), so:
SELECT SUM(fi.etiliquido)
FROM fi
WHERE fi.fno IN (SELECT d.val
FROM divideString( (SELECT TOP 1 REPLACE(CAST( u.nrdoc AS nvarchar(max)), '/', ',')
FROM u_ups1 as u
WHERE 1057 IN (SELECT d.val
FROM divideString(REPLACE(CAST(u.nrdoc AS nvarchar(max)), '/', ',') d(val)
)
)
) d(val)
);
Also, using TOP with no ORDER BY is usually suspicious.
Storing multiple values in a single column is not recommended. However, I don't think you need a table-valued functions for this. LIKE should work:
SELECT SUM(fi.etiliquido)
FROM fi
WHERE EXISTS (SELECT 1
FROM (SELECT TOP 1 u.nrdoc
FROM u_ups1 u
WHERE '/' + u.nrdoc + '/' LIKE '%/1057/%'
) u
WHERE '/' + u.nrdoc + '/' LIKE '%/' + fi.fno + '/%'
);
And what you might want:
And, the logic that you want might be as simple as this:
SELECT SUM(fi.etiliquido)
FROM fi
WHERE EXISTS (SELECT 1
FROM u_ups1 u
WHERE '/' + u.nrdoc + '/' LIKE '%/1057/%' AND
'/' + u.nrdoc + '/' LIKE '%/' + fi.fno + '/%'
);