Question

I have array of strings. For example 10 strings in array FileNamesArray[]

I have a DB table that contain 7 rows. MyFiles table description:

ID int
FileName varchar

I want to know which of strings from array doesn’t exist in my table.
Smth like this:

    "SELECT * FROM (" + FileNamesArray + ") LEFTJOIN MyFiles ON FileNamesArray = MyFiles.FileName WHERE MyFiles.FileName IS NULL

How to express it in SQL?
Can I avoid temp tables?

P.S. Example

FileNamesArray = ['file1', 'file2', 'file3', ..., 'file10']
MyFiles = ['file0', 'file1', ..., 'file6']
I need to get answer = ['file7', 'file8', 'file9', 'file10']

Answer 1

If you filenames are fixed you could declare an memory table, so for example

DECLARE @Temp TABLE (
  Filename VARCHAR(255)
)

INSERT INTO @Temp VALUES ('file1')
INSERT INTO @Temp VALUES ('file2')
INSERT INTO @Temp VALUES ('file3')
INSERT INTO @Temp VALUES ('file4')
INSERT INTO @Temp VALUES ('file5')
INSERT INTO @Temp VALUES ('file6')
INSERT INTO @Temp VALUES ('file7')
INSERT INTO @Temp VALUES ('file8')
INSERT INTO @Temp VALUES ('file9')
INSERT INTO @Temp VALUES ('file10')

SELECT t.Filename
FROM @Temp t
LEFT JOIN MyFiles mf ON t.Filename = mf.Filename
WHERE mf.Filename IS NULL

I can’t see how you could get away from using a temp table, hope this helps