VO & Ado
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From: jorgeaccinelli on 20 Apr 2008 13:13 On 20 abr, 12:54, Lars Broberg <this.is.not.a.va...(a)dress.se> wrote: > Jorge, > > Finally ... > > MY RECORDET is in read-only mode, but another > > user can take the same recorset in mode > > Read- write and change things? When I update the > > Database should I take precautions > > If this has happened? I guess the answer, > > But I am planning to move from DBF to Sql > > I would like to know your opinion > > Thanks > Well, there are no locks held and no "connection" to the database (if > you have a clientside cursor) so you have no idea what's happening there > <g>. > But the locking strategies in SQL really isn't any different from DBF, > but you have the option to do the updates/inserts/deletes in a couple of > different ways: > - Via ADO (obviously not with ReadOnly recordsets) > - Via your own "UPDATE/DELETE/INSERT" code executing via AdoCommand > - Via your own Stored Procedures (for UPDATE/DELETE/INSERT) > In the first case ADO can handle the lockings if you have a primary key > in the table and you use for example adLockOptimistic. I wouldn't use > this other than for very simple updates on simple tables. > In the two other cases you have to have some way of "knowing" if some > other user have changed the record before "you". The term "record" here > can mean information from more than one table. You normally use datetime > fields for this or the SQL Server Timestamp data type. > Some info about the Timestamp data type:http://msdn2.microsoft.com/en-us/library/ms182776.aspx > Hope this helps in some way... > ---- > Lars Broberg > Elbe-Data AB > lars at elbe-data dot se Thank you, the answer is very useful Jorge
From: Rob van Erk on 20 Apr 2008 15:03 Erik, Willie, Thanks for your comments on the subject. Removing the ..close() solved the issue but also changed my code and used the SetRecordSet instead. All clear. Geoff, Frankly speaking I have to learn much more on SQL. I succeed now to insert, delete and update records and that is for me a big step forward. Same story for the "why do you use the forward cursor" remark you made. The background and usage of a "cursor" was explained in one of the previous messages but not yet sure when to use what. Anyhow, thanks for the info. Brgds, Rob
From: Geoff Schaller on 20 Apr 2008 17:36 Rob, Like all things, you need to look them up and you should not be relying on this forum for such fundamental answers to SQL matters. If you want to learn about cursors and you don't get enough out of the book on your desk then look it up in Books On Line (BOL) for SQL Server. They are very good. Search on cursor and you will get several pages explaining all the types of cursors and even when to use them. After BOL you need google. Again, type cursor <enter> and a wealth of definitions and discussions arise. The kinds of questions you are asking indicate that you need to know more about the fundamentals of SQL first because you aren't really asking the right questions. As a result you only get half-answers in a forum like this one. SQL has come a long way in 5 years and will offer you things DBF just cannot imagine. But it also comes with issues of its own and if you don't understand these, they will bring you undone very quickly. Or best case, you will never achieve what SQL offers. Read up on SQL first and get to understand the DBMS engine. Then ask the questions <g>. Geoff "Rob van Erk" <erk.v(a)hotmail.com> wrote in message news:c38a57ae-60e2-4aa5-91c1-b388cc5e320c(a)l64g2000hse.googlegroups.com: > Erik, Willie, > > Thanks for your comments on the subject. Removing the ..close() solved > the issue but also changed my code and used the SetRecordSet instead. > All clear. > > Geoff, > > Frankly speaking I have to learn much more on SQL. I succeed now to > insert, delete and update records and that is for me a big step > forward. Same story for the "why do you use the forward cursor" remark > you made. The background and usage of a "cursor" was explained in one > of the previous messages but not yet sure when to use what. Anyhow, > thanks for the info. > > Brgds, > Rob
From: Rob van Erk on 21 Apr 2008 01:22 Geoff, Will have a look at BOL. Some months ago I purchased two dutch SQL books and basically I already made a lot of progression understanding the SQL logic (including DBMS). My app runs fine with information gathered from these books but in practise you will always find new challenges like the "cursor" thing. Will study further but as programmer you always like to practise/play in your applications too... Rob
From: Geoff Schaller on 21 Apr 2008 02:17
Sure... and cursors can be your 'curse' <g>. Mostly, for VO style uses (particularly browsers), client side static cursors are the go. But forward only, server side read only cursors can be very fast for lookups. The degree of locking can have a huge impact on performance. It all matters so it is all quite relevant. Geoff "Rob van Erk" <erk.v(a)hotmail.com> wrote in message news:800f9edd-a459-449c-92fb-348867cc88fa(a)b1g2000hsg.googlegroups.com: > Geoff, > > Will have a look at BOL. Some months ago I purchased two dutch SQL > books and basically I already made a lot of progression understanding > the SQL logic (including DBMS). My app runs fine with information > gathered from these books but in practise you will always find new > challenges like the "cursor" thing. Will study further but as > programmer you always like to practise/play in your > applications too... > > Rob |