Re: Some Miscellaneous Questions on 4GL

Path: emory!europa.asd.contel.com!darwin.sura.net!jvnc.net!yale.edu!think.com!sdd.hp.com!hplabs!pyramid!infmx!jacob From: jacob@informix.com (Jacob Salomon) Newsgroups: comp.databases.informix Keywords: informix scroll cursor Message-ID: <1991Dec26.205827.14561@informix.com> Date: 26 Dec 91 20:58:27 GMT References: <1991Dec26.161921.9278@cbnews.cb.att.com> Sender: news@informix.com (Usenet News) Organization: Informix Software, Inc. In article <1991Dec26.161921.9278@cbnews.cb.att.com> mvctm@cbnews.cb.att.com (carl.t.mosley) writes: |I have some questions on writing 4GL apps....I am using 2.10 for DOS: | |I would really like to use a scroll cursor for handling query results |but allowing the user to "fetch previous" gets confusing if they also |have the ability to do a delete because the delete is done on the |table in the database and not in the temporay place where the scroll |cursor data is kept. The manual says to not use scroll cursors for |this reason - has anyone worked around this? It seems that in the SQL |product, when you "run" a form, you are using some kind of ready-made |scroll cursor for "Next" and "Previous" on the menu and yet if you |"Remove" the current row it is gone from the active set also. | |Thanks |Carl Mosley AT&T NS |ctm@mvune.att.com Hi Carl and all other interested eavesdroppers. I have used the following to get around the problems you describe. Bear in mind, however, that I am giving you a simplistic start. For multi-table queries or ordering of data, the technique needs some refinement. DEFINE row_array[1000] INTEGER, lc SMALLINT CONSTRUCT <query> ON <fields> LET string = "SELECT rowid from <table> WHERE ", <query> PREPARE prep_sql FROM string DECLARE prep_curs CURSOR FOR prep_sql LET lc = 0 FOREACH prep_curs INTO row_array[lc + 1] LET lc = lc + 1 END FOREACH MESSAGE lc " rows retrieved" # Just to show you a counter LET row_num = 1 SELECT * INTO data_rec.* FROM table WHERE rowid = row_array[1] ... down to the menu part. ... COMMAND "Next" "Get the next record" LET row_num = row_num + 1 SELECT * INTO data_rec.* FROM table WHERE rowid = row_array[row_num} DISPLAY BY NAME data_rec.* You should get the idea; using a fixed array of rowid's, it is easy to delete an element from the array when you delete the corresponding row in the table. As I said, this is a simplistic way of doing it; you can use a cursor to fetch the record instead of a whole new SELECT. As it stands, this will not order the retrieved data; that's for you to refine, normally using a dummy variable to get the column you are ordering by. If it's a view, I wash my hands of you. Otehrwise, do try it; I have written nearly 2 dozen applications using this technique. It works, within it's limitations. -- Jake Salomon --- Disclaimer: This in IMO only; not necessarily endorsed by my employer. -- ----------------Obligatory smart-$$$ remark:--------------------- | There's two kinds of people: Those who categorize people into | | two groups and those who don't. (Aging proverb.) | -----------------------------------------------------------------