in reply to Re^2: Multiple DB Queries using DBI
in thread Multiple DB Queries using DBI

It's straight out of the DBI docs:

Portable applications should not assume that a new statement can be prepared and/or executed while still fetching results from a previous statement.

I do not have personal experience with using Perl to talk with MS SQL or Oracle databases, but I know for sure that only one query can be active at a time per MS SQL database connection in VB. My coworker has said the same for Oracle (using an unspecified language other than VB and Perl).

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Re^4: Multiple DB Queries using DBI
by dragonchild (Archbishop) on Nov 18, 2004 at 19:40 UTC
    I know that for Oracle and MS SQL (which is the same as Sybase, for all practical purposes), you can have multiple sths executing at once. Heck, without that for Oracle, a lot of Perl code would mysteriously break. :-)

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[reply]
      DBD::ODBC did not used to allow multiple active statement handles (because ODBC did not allow it). Support for it was added in DBD::ODBC 1.08 if you use odbc_cursortype => DBI::SQL_CURSOR_DYNAMIC on the connect (and it only says it "may allow some servers" to support multiple concurrent statements).
[reply]
[d/l]
      updated: changed "physical" to "network" connections.

      With DBD::Sybase multiple active $sth require multiple physical network connections.

      There is a way to have multiple simultaneous queries active on a single connection by using client side cursors, but this seriously limits the type of queries that can be sent so I didn't implement it.

      That said - you can have multiple $sth open at the same time as long as only one is active at a time (meaning that it has been executed and that not all results have been fetched yet.)

      Michael

[reply]

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