Movatterモバイル変換

mysqldb simple question (find unique number)

• Previous message (by thread):RS232 module
• Next message (by thread):mysqldb simple question (find unique number)
• Messages sorted by:[ date ][ thread ][ subject ][ author ]

"Jacek Pop³awski" <jp at ulgo.koti.com.pl> wrote in messagenews:slrn9eckbh.2f7.jp at localhost.localdomain...> id_producenta is primary key (int) for table producent> I need to find unique value for it, I use that code:>>     dbh.query('select id_producenta from producent');>     res=dbh.store_result()>     how=res.num_rows();>     id=[]>     for i in range(how):>       r=res.fetch_row()>       id=id+[int(r[0][0])]>     del res>     return max(id)+1;>> Looks quite long... how to write it in better way?>MySQL implements the max() SQL function.Your current code has your database client program scanning all rows to findthe maximum value. Try something along the lines of (untested):dbh.query('select max(id_producenta) from producent')res = dbh.store_result() # should only be one row!m = int(res.fetch_row()[0])return m+1Of course, you will realise that problems might arise should any two usersconcurrently try to use any such routine, since NySQL (as far as I remember)does not support transactions.regards steVe

• Previous message (by thread):RS232 module
• Next message (by thread):mysqldb simple question (find unique number)
• Messages sorted by:[ date ][ thread ][ subject ][ author ]