Re: database independence

> We are in the planning stages for development of a brand new product. This > product will be Unix based and will use A database as a data store. One of > the questions we are grappling with is whether or not we want to attempt to > be "database independent". By "database independent" we mean supporting a > limited number of rdbms vendor's products such as Ingres, Informix, Oracle and > Sybase. Since many of our customers may already have a database of choice, it > would be nice if we could simply cut an Oracle version of the product or a > Sybase version of the produt from the same loadline. > My question is "What type of issues would be involved to acheive this level > of independence?". It is my understanding that the ANSI SQL standard sets > specific guidelines for embedded SQL. It is also my impression that most > vendors attempt to conform to this standard, adding their own extensions of > course. Is it then reasonable to assume, at least in the case of embedded SQL, > that such "independence" could be acheived with minimal difficultly? I could > envision some syntatical differences between the implementations that would > require an occassional #ifdef, but I would hope that the majority of the > statements could be reused. > In terms of the database itself, I am assuming that if we use the lowest > common demonitor of the SQL-92 standard which is implemented by all vendors, > then the schema would be fairly portable as well. Again, it may be reasonable > to have product specific schemas which take advantage of a particularly useful > feature or conversely accounts for some anomoly or divergence from the standard. > So tell me...have I been sniffing too much model airplane glue?!?! I know there > has to be more to it than what I have outlined above. What am I overlooking? > I would love to hear from anyone on this subject, especially if you have tackled > this "independence" issue yourself. We are writting an ESQL/C application (that also uses OSF/DCE) that is database independant and hardware independant. We are writting to the ANSI-92 SQL Entry Level standard, which most vendors expect to have available Q1 of 1994. I sent a survey to Informix, Digital, Oracle, Ingres, and Sybase to ask them how they handled certain things. There are some Intermediate Level statements that we found are supported by all vendors, which we are also using. Our ESQL/C code is totally vendor independant except for one file, which contains certain syntax differences (defined as MACROS). Since these vendors don't all conform yet to even Entry Level, this allows us to specify any current syntax. There are certainly tradeoffs when choosing to be this open. There are certain Informix enhancements I would love to take advantage of, but cannot since the other vendors do no support them. There are also locking issues that you must consider, since the specific implementation of the isolation levels is left up to the vendor. There are many more issues involved. If you would like to discuss further, feel free to contact me. Good Luck! ------------------------------------------------------------------------------ John M. Shoemaker internet: shoemaker@tweety.digsys.com Daugherty Systems UUCP: uunet!fms2000!johns One City Place, Suite 240 FAX: (314) 432-8217 St Louis, MO 63141 Voice: (314) 432-8200 ------------------------------------------------------------------------------ EXEC SQL include "disclaimer.h"; ------------------------------------------------------------------------------