How can I copy records between tables only if they are valid according to check constraints in Firebird/Interbase?

Question

I want to copy a bunch of records from a temp table to a target table. The problem is that some records may violate check constraints in the target table so I want to insert everything that is possible and generate error logs somewhere else for the invalid records.

If I execute:

INSERT INTO target_table
  SELECT ... FROM temp_table

nothing would be inserted if any record violates any constraint. I could make a loop and manually insert one by one, but I think the performance would be lower.

Answer 1

Like this:

INSERT INTO
    some_table1 (fld1, fld2, fld3)
SELECT
    some_table2.fld1,
    some_table2.fld2,
    some_table2.fld3
FROM
    some_table2
WHERE
    some_table2.fld > 100
LIMIT
    5;

Answer 2

You could write an stored procedure which copyes the records and catches any error with WHEN ANY DO statement, something like

CREATE PROCEDURE CopyRecords( ... )
AS
BEGIN
  FOR select ... FROM temp_table INTO ... DO BEGIN
     INSERT INTO target_table ...
     WHEN ANY DO BEGIN
        INSERT INTO ErrorLog(SQL_Code, GDS_Code, ... ) VALUES(SQLCODE, GDSCODE, ...);
     END
  END
END

The WHEN ... DO statement is documented in InterBase 6.0 Language Reference (scroll down the page, the IB 6 doc downloads are at the bottom), under "Procedures and Triggers" chapter.

The GDSCODE and SQLCODE context variables should help you to analyse what is exactly the reason of the error.