Arthur Fuller
artful at rogers.com
Sun Dec 18 13:01:15 CST 2005
As usual, JC is right. I would the following: search your front end for record and row sources that begin with the word "SELECT" and convert all instances to named queries before doing the upsize. Then these will convert as well, without the converter giving them incomprehensible names. You may also have code that dynamically constructs SQL statements using the values of form controls. This is harder to fix, but in general (depending on your convention) the string in question is called strSQL or maybe sSQL or whatever. The way to locate this is to look for the command below the statement's construction: DoCmd.RunSQL <strSQL>. If you are serious about doing the conversion, then you want to isolate these instances, consider whether they can be converted to stored procedures -- and if so, convert them, and if not, tough luck; identify them as potential bottlenecks and proceed. <rant> There are a VERY few occasions in which dynamic SQL construction is required. In my experience, almost all occasions in which it is used are due to the lack of analysis on the part of the programmer. A stored procedure or table-UDF will execute much more quickly than its equivalent dynamically-constructed SQL statement, since there is no way that such a statement can be optimized. I have repeatedly encountered the objection that "I may or may not have parameters x, y and z, the user may have chosen only one or two". This objection is fallacious. The way to handle this possibility in a stored procedure is to compare the parameter to itself, as this snippet illustrates: SELECT * FROM myTable WHERE AccountNumber = @AccountNumber OR @AccountNumber IS NULL You can perform this logic for any set of parameters that might be passed. If you don't believe me, try it. I am converting a colleague's app from MDB to SQL currently, and the MDB contains about 100 occurrences of this sort of code. A form has several controls on it, any combination of which might be used to create a filter. There are dozens and dozens of lines of code that anticipate that this one is null and the other two are not, etc. It is all silly, in both Access and SQL. In SQL the simplest thing to do is to pass all the values of all the relevant controls as parameters to the stored procedure, and let it deal with nulls as outlined above. Dozens or hundreds of lines of code disappear, replaced by one call to the stored procedure. In an MDB you need static functions to achieve the same, but that`s cool. Typically, you create a query that selects this and that from somewhere. You can name it and save it, but the problem is that you cannot conveniently pass parameters to it. If you could, the code would reduce to one line approximately; but you cannot, so the most common practice is to dynamically build an SQL statement and run it instead. Numerous lines of code construct a statement then passed to DoCmd.RunSQL. This is nonsense, IMO. Let us suppose that a given query requires 3 parameters, any or all of which might be passed. Let us call them Country, Region and Customer. Suppose that the front lets the user select any combination of these controls, such that Country only results in a list of every customer in that country, and so on. Create a static function that gets or sets the value for each of these: call them CurrentCountry, CurrentRegion and CurrentCustomer. Each of these is written to return a numeric value, either zero or greater than zero (which presumably references the PK of some other related table). Then write the query invoking these functions rather than addressing the particular form of interest. Modify the query slightly so that at the end of the day it resembles this: SELECT * FROM somewhere WHERE Country = CurrentCountry() OR CurrentCountry() = 0 AND Region = CurrentRegion() OR CurrentRegion() = 0 AND City = CurrentCity() OR CurrentCity() = 0 --------------------- I wrote this in Outlook, whose syntax checker does not extend to Access, but I hope this illustrates my points: a) There is NO need to reference specific forms to obtain specific values to plug into queries. b) By wasting your time constructing dynamic SQL queries, you make your code tough to decipher and also bill the client for unnecessary hours. c) By creating the static functions to plug into your query, you enable said query to be used in numerous situations. You can even run it from the debug window with no forms open. Just call the static functions in Set mode then run the query. No need to open the form or report. You will see the results immediately, and if they are wrong then fix the query not the form or report. d) on the chance that you might have to convert an MDB to SQL, queries written this way are easy to port. Static functions can`t be used in SQL of course, but the query itself can be changed to refer to arguments in an equivalent stored proc or table UDF. Estimated conversion time: 1 minute per instance. And finally, the more you do this, the better you will like it. </rant> Sorry for the length of the rant, but once I get started watch out! LOL. A. -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of John Colby Sent: December 16, 2005 3:47 PM To: 'Access Developers discussion and problem solving' Subject: Re: [AccessD] Upsize? Pull ALL of the tables into a single db, set the relationships, upsize, fix errors, upsize, fix errors, repeat until it goes. John W. Colby www.ColbyConsulting.com