SQL - safely downcast BIGINT to INT

Question

I have a CSV I\'m importing into our database. One of the \"columns\" contains data that should be an INT but some rows have numbers that only fall in the BIGINT ra

Answer 1

Cast your bigint to varbinary, then store the lower half to @UserID and check the upper half:

• if the upper half is all 0's and the lower half represents a non-negative value, @UserID then contains the correct int value;

• if the upper half is all 1's and @UserID is negative, it's all right too;

• otherwise there's an arithmetic overflow.

Here's an implementation:

DECLARE @UserIDBigInt BIGINT = 9723021913;
DECLARE @UserID INT, @HighInt INT;

WITH v AS (SELECT CAST(@UserIDBigInt AS varbinary) AS bin)
SELECT
  @HighInt = SUBSTRING(bin, 1, 4),
  @UserID  = SUBSTRING(bin, 5, 4)
FROM v;

IF (@HighInt = 0 AND @UserID >= 0 OR @HighInt = -1 AND @UserID < 0) BEGIN
    SELECT 'Handle it as reliable data'
END