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Suppose you have a DB table like this:

Table t .... column_a integer column_b varchar(255) ....

Now, I want to store a string that is composed by a list of names on t.column_b, with the following format (separated by commas):

Word A, Word B, Word C...

The problem is, it might be the case that the string is larger than 255 characters and in my application logic I don't want to blindly trim to 255, but instead store the maximum number of words possible, eliminating the last word that exceeds the size. Also, I want to develop in such a way that if the column changes size, I don't want to change my application. Is it possible to write a SQL query that retrieves the declared size of a column? Or perhaps, I should use another column type?

If relevant, I am using Informix.

Thanks in advance.

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  1. Informix truncates blindly at the limit unless your database is MODE ANSI.

  2. The DBI defines metadata attributes for columns and DBD::Informix implements them.

    For a statement handle, $sth, you can use:

    $sth->{PRECISION}->[0]

    to get the precision (length) of the first column in the output.

See perldoc DBI under 'Statement Handle Attributes'.

If you need to know the type information for some column, write a SELECT statement, prepare it, then analyze the statement handle.

Because this is defined by DBI, you will get the same behaviour with any driver (DBD::YourDBMS).

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