On 12/07/11 13:04, ZhangJun wrote:
mostly I use mysql, DBD::mysql, also mssql, ODBC and sybase driver.
I cannot comment on DBD::mysql (as it has been years since I last used it) but both MS SQL Server and Sybase (I believe) don't support multiple active statements on the same connection unless you enable something like the new MARS support in MS SQL Server (but it has other disadvantages). I wrote a small document for DBD::ODBC at http://www.easysoft.com/developer/languages/perl/multiple-active-statements.html which describes the issues and workarounds. Multiple Active Statements (MAS) are more than one statement in the same connection that have active work (or result-sets, Multiple Active Result Sets (MARS)). If you are writing code which may connect to multiple DBDs then I'd avoid multiple active statements. Often they can be avoided by a simple reorganisation of your SQL. If you absolutely have to have them then you can use multiple connections but this also has other disadvantages. Personally, I try to avoid them as much as possible and usually find the code using multiple active statements can be rewritten to use one. But basically, I'm just repeating what is in the document referenced above. Martin -- Martin J. Evans Easysoft Limited http://www.easysoft.com
