Recognizing invalid dates in postgresql

问题

I am trying to parse dirty input into postgres tables. I have a problem with a 'date' field occasionally containing non-dates such as '00000000' or '20100100'. pg refuses to accept these, and rightly so.

Is there a way to have postgres recognize invalid dates (or only valid dates, if that works better), so I can substitute a sensible default?

(I've considered building a table listing the dates I'm willing to accept, and use that in a sub-select, but that seems awfully inelegant.)

Cheers,

Jurgen

回答1:

http://www.tek-tips.com/viewthread.cfm?qid=1280050&page=9

A more generic approach than the above:

create function safe_cast(text,anyelement) 
returns anyelement 
language plpgsql as $$ 
begin 
    $0 := $1; 
    return $0; 
    exception when others then 
        return $2; 
end; $$;

Used like this:

select safe_cast('Jan 10, 2009', '2011-01-01'::timestamp)
select safe_cast('Jan 10, 2009', null::timestamp)

Credited to the friendly dudes at the #postgresql irc channel. :)

回答2:

You could write a pgsql function with an exception handling block.

来源：https://stackoverflow.com/questions/6730095/recognizing-invalid-dates-in-postgresql