check bind_columns for undefined values

gropey has asked for the wisdom of the Perl Monks concerning the following question:

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Re: check bind_columns for undefined values by ikegami (Patriarch) on May 17, 2011 at 18:31 UTC
Your question isn't clear	[reply]
Re: check bind_columns for undefined values by Neighbour (Friar) on May 18, 2011 at 08:56 UTC
Why would you want to replace undef values (which correspond to NULL-values in the database) with the string "null" anyway? That can change the datatype of the column (since numeric columns can also contain NULL values, which you change to a text datatype). To answer your question, if you use `$sth->bind_columns(\$var1, \$var2, \$var3);` [download] You'd have to check all vars to see if they're undef after fetching data and act accordingly. This method might make things simpler: `@list_of_refs_to_vars_to_bind = (\$var1, \$var2, \$var3); $sth->bind_columns(@list_of_refs_to_vars_to_bind);` [download] Now you can use `map { $$_ = "null" if (!defined $$_); } @list_of_refs_to_vars_to_bind;` [download] to do your evil thing.	[reply] [d/l] [select]
Re^2: check bind_columns for undefined values by Anonymous Monk on Feb 12, 2013 at 00:35 UTC
Hi, Thanks for the Map idea, I'm new to perl (but not other similar languages). Can someone explain why the example: map { $$_ = "null" if (!defined $$_); } @list_of_refs_to_vars_to_bind; ...uses $$_ when I would expect it to use $_ - i've googled round and round but haven't found an explanation yet. many thanks jonathan	[reply]
Re^3: check bind_columns for undefined values by ww (Archbishop) on Feb 12, 2013 at 02:51 UTC
A decent tut on reference/dereference -- such as those found in Tutorials right here in the Monastery -- should make the answer clear. If you didn't program your executable by toggling in binary, it wasn't really programming!	[reply]