RE: Blobs: How to tell when I retrieved a null blob

1) Locate the blob in memory and and let it=null 2) you can use the "is null" test in boolean expressions both in sql (=where clauses) and 4gl statements. A word of warning. Don't test blob variables unless you have located them. A "let test=var is null" evaluates to *false* (I have tested this - you also get a -450 error, btw) if var has not been located; once var has, the test behaves sensibly, that is yelds true if it has been located in memory or a non existing file, and false if the file exists or after you select something in it. HTH, Marco ____________________________________________________________________________ rem radioterapia, which I immeritately manage, seldom agrees with what I say marco greco (Catania, Italy) Work: marcog@ctonline.it rem radioterapia 39 95 447828 fax 446558 (was mar.greco@agora.stm.it) Achea 39 95 503117 --- On Thu, 13 Feb 1997 10:17:37 GMT Jacob Salomon <jake@apparel.net> wrote: Hi folks, 2 questions, after verbose explanation. I am writing a small program to insert & retrieve blobs. Right now it's very simple: When a user wants to insert a blob, they type the name of a .gif file in a field in the form. My program LOCATEs the blob variable in the file and does the insert. If the user omits the file name, I still do the insert but first I locate the blob variable in /dev/null. I have confirmed that when I locate in /dev/null, the onstat -d shows no fewer free blob pages. So this works, though I'm sure there is a better way. My first weustion is: 1. Is there something I can do in 4GL to specify a null location, so that my code won't even bother opening /dev/null? (For that matter, are the 4GL library functions smart enough to recognize /dev/null and skip opening it already?) Next is the issue of how I recognize a null blob when I read it back in. For now, I have hard coded the location before fetching the blob i.e. Before fetching it I code: LOCATE blobvar IN FILE "yutz.blob" FETCH blobcurs INTO blobvar 2. How can I recognize when the blob data is null? In ESQL I could look at the length member variable of the locator structure (I think) but what do I look at in 4GL to see a 0-length? BTW, when I do the retrieval, I can see that the file "yutz.blob" is indeed 0 bytes long. I don't see anything in the sqlca that would warn me. Thanks much. -- -- Jake (With a non-zero supply of hot air) . . _..-'( )`-.._ ./'. '||\\\\. }\\_/{ .//||` .`\\. ./'.|'.'||||\\\\|.. )o o( ..|//||||`.`|.`\\. ./'..|'.|| |||||\\`````` \\,@,/ ''''''/||||| ||.`|..`\\. ./'.||'.|||| ||||||||||||. ||| .|||||||||||| ||||.`||.`\\. /'|||'.|||||| ||||||||||||{ | }|||||||||||| ||||||.`|||`\\ '.|||'.||||||| ||||||||||||{ | }|||||||||||| |||||||.`|||.` '.||| ||||||||| |/' ``\\||`` | ''||/'' `\\| ||||||||| |||.` |/' \\./' `\\./ \\!|\\ /|!/ \\./' `\\./ `\\| V V V }' `\\ /' `{ V V V \\ \\ \\ V / / / +-----------------------------------------------------------+ | Impeccable Logic: A thought process which successfully | | resists chicken bites | +-----------------------------------------------------------+ -----------------End of Original Message-----------------