very thank you !:) if i have more question will ask you again.
thank you again! > Subject: RE: about use Dev-cpp and C++ > > > what's nested SQL? > > can you tell me more about it? > > Nested SQL allows you to do all kinds of interesting things in MySQL > that you can't do now - sub-selects, for example; or if you're a lazy > programmer (like me!) you want to do grouping and sorting in ways that > would be difficult (and complicated) with an ordinary SQL query. > > For example, suppose you had two tables - a users table and a messages > table. You suspect that you've got orphaned records in the messages > table, but you're not sure. You also want to do other stuff to each > message as you go through it. So, you decide that you want to iterate > through each record in the users table, setting a flag in the messages > table for each message that isn't orphaned: > > char cmd[256]; > > /* you could also do an ExecuteSQL() here, too */ > OpenRecordset("update messages set OK='N'"); > CloseRecordset(); > /* or ExecuteSQL ("update messages set OK='N'"); */ > OpenRecordset("select * from users"); > while(RecordsetEOF() != EOF) > { > /* ID in the users table has a one-to-many relationship to usersID > in the messages table */ > sprintf(cmd, "update messages set OK='Y' where usersID=%s", > GetField("ID")); > OpenRecordset(cmd); > CloseRecordset(); > /* could also do a ExecuteSQL(cmd); */ > MoveNext(); > } > CloseRecordset(); > /* now, we want to see which records are orphaned */ > OpenRecordset("select * from messages where OK='Y'"); > while(RecordsetEOF() != EOF) > { > /* do whatever here */ > MoveNext(); > } > CloseRecordset(); > > Of course, this is a simple example. PLEASE DON'T POST QUERIES SHOWING > HOW THIS COULD BE DONE EASIER OR FASTER OR WHATEVER IN SQL! I'm sure > you can think of a lot of other examples where doing a sub-select would > be very cool, but MySQL doesn't support it. > > sql, query --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php