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Asked: 2026-05-22T14:15:08+00:00

I must import lines from a file into database. I must check if foreign

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I must import lines from a file into database. I must check if foreign key exists. Here a sample of lines I should import :

A   481 11/23/1981  12  77000   DESCRIPTION_1     $5,098
A   482 11/23/1981  15  77000   DESCRIPTION_1     $5,098    
A   482 11/23/1981  12  77000   DESCRIPTION_1     $5,098
A   481 11/23/1981  9   77000   DESCRIPTION_1     $5,098
A   481 11/23/1981  12  77000   DESCRIPTION_1     $5,098
A   481 11/23/1981  12  77000   DESCRIPTION_1     $5,098
A   481 11/23/1981  1   77000   DESCRIPTION_1     $5,098
A   481 11/23/1981  1   77000   DESCRIPTION_1     $5,098
A   481 11/23/1981  1   77000   DESCRIPTION_1     $5,098
A   481 11/23/1981  1   77000   DESCRIPTION_1     $5,098

Here the foreign key are 12, 15, 9, 12, 1. I want to check if one of these foreign key. In the sample the foreign key 12 does not exist. The simplest way is to test line by line : 

SELECT COUNT(*) From TypeTable WHERE IdType = 12 -- 0
SELECT COUNT(*) From TypeTable WHERE IdType = 15 -- 1
SELECT COUNT(*) From TypeTable WHERE IdType = 9  -- 1
SELECT COUNT(*) From TypeTable WHERE IdType = 12 -- 1
SELECT COUNT(*) From TypeTable WHERE IdType = 1  -- 1

The problem with this method is that there is one query for each different foreign key, and files I should import has thousands lines (and potentially thousands foreign key).

So I want to know if it’s possible to use the “set feature of SQL” to retrieve in one query but I don’t know how to do this…

PS : In the result of my query, I need to know the foreign key does not exist in database

Regards,

Florian

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1 Answer

  1. Editorial Team

    If the data has been loaded into a staging table then you can use this

    SELECT
    *
FROM
   myStagingTable ST
WHERE
   NOT EXISTS (SELECT *
            FROM TypeTable TT
            WHERE ST.FKCol = TT.IdType)

    To do something set based, you need a table with the desired FK values. This could be a temp table on the same connection and populated by scanning the file. The same SQL would work above by changing myStagingTable to #myFKTable

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