I’m writing a service in Nestjs which uses typeorm to communicate with a MySQL server. Say, I create a table, test_table with two columns col1 and col2, col1 having a UNIQUE constraint.

If try to insert a duplicate value I get an error which looks like:

{
  query: 'INSERT INTO `test_table`(`col1`, `col2`) VALUES (?, ?)',
  parameters: [ 'test-val-1', 'test-val-2' ],
  driverError: {
    code: 'ER_DUP_ENTRY',
    errno: 1062,
    sqlState: '23000',
    sqlMessage: "Duplicate entry 'test-val-1' for key 'test_table.col1'",
    sql: "INSERT INTO `test_table`(`col1`, `col2`) VALUES ('test-val-1', 'test-val-2')"
  },
  code: 'ER_DUP_ENTRY',
  errno: 1062,
  sqlState: '23000',
  sqlMessage: "Duplicate entry 'test-val-1' for key 'test_table.col1'",
  sql: "INSERT INTO `test_table`(`col1`, `col2`) VALUES ('test-val-1', 'test-val-2')"
}

If I return sqlMessage it exposes the table name and column name, I don’t get the name of the erroneous column explicitly.

Is there a way to extract information in a format such that I can have the column name which is causing the error and what error is it causing?

There are two solutions I can think of:

• Checking for duplicate entry by hitting the db before trying to insert. It will increase latency because of additional database calls.

• Or I can write a parser which extracts the relevant information from the message but it seems like going overboard because if the message changes for some reason, it breaks.