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SQL Related Articles: Better SQL Part 10 2002-10-29 -- Dan Pressnell When you use the Clarion ODBC driver in your program, you get one connection
(to a server) at a time. With the MSSQL driver, though, you can connect to
different servers at the same time. It might be possible with other Clarion
native SQL drivers, but I don't know about that.
Let's say your program needs to establish and maintain two connections at the same time, and you are going to use the CWODBC object that is at http://www.icetips.com/downloadfile.php?FileID=59. The trick to doing this is to write a little code to use the flexibility of an INTERFACE (remember that the cwodbc object is written as an interface). I'll go into interfaces elsewhere at another time. But I'll illustrate here how to make two simultaneous connections to MSSQL servers. You need two procedures that you write yourself. Don't worry, the code is short. Here are the two procedures. First, the prototypes:
map
NewServerAConnection(), *cwodbc
NewServerBConnection(), *cwodbc
end
Now for the code for each procedure:
NewServerAConnection procedure
MyFile file, driver('mssql')
record ! use fields if you want;
! this is for illustration
end
end
conn &cwodbc
code
myfile{prop:owner} = 'ServerA,mydatase'
conn &= newcwodbc()
conn.setfile(myfile)
conn.settableinfo('sometablename', 'somefieldname')
return conn
NewServerBConnection procedure
MyFile file, driver('mssql')
record ! use fields if you want;
! this is for illustration
end
end
conn &cwodbc
code
myfile{prop:owner} = 'ServerB,mydatase'
conn &= newcwodbc()
conn.setfile(myfile)
conn.settableinfo('sometablename', 'somefieldname')
return conn
Now when you want to query something on ServerA, you create an instance of
the cwodbc object like this:
sql &= newServerAConnection()
! your code here
sql.Release()
When you want to query something on ServerB, the code is very similar:
sql &= newServerBConnection()
! your code here
sql.Release()
Although you can't maintain two simultaneous connections with the ODBC
driver, this technique can come in handy with ODBC anyway. Say you want one
object that will handle queries that don't return TEXT, IMAGE, and other
large type fields, and you want one that is optimized for speed, but won't
handle such fields. They you write two procedures like this:
NewSpeedySQL procedure
MyFile file, driver('odbc')
record
cstring(256)
cstring(256)
cstring(256)
cstring(256)
cstring(256) ! add as many of these as
! you will need to handle
! your largest column count
! (Press Ctrl-2)
end
end
conn &cwodbc
code
myfile{prop:owner} = 'myconnectstring'
conn &= newcwodbc()
conn.setfile(myfile)
conn.settableinfo('sometablename', 'somefieldname')
return conn
NewBlobSQL procedure
MyFile file, driver('odbc')
record
end ! use NO fields in this
! one, so it can handle
! large columns, and any
! number of columns
end
conn &cwodbc
code
myfile{prop:owner} = 'myconnectstring'
conn &= newcwodbc()
conn.setfile(myfile)
conn.settableinfo('sometablename', 'somefieldname')
return conn
Now when you want a speedy cwodbc object, you create it like this:
sql &= newSpeedySQL()
And when you want one that handles large type columns, like this:
sql &= newBlobSQL()
Today is November 21, 2024, 3:42 am This article has been viewed 35266 times. Google search has resulted in 81 hits on this article since January 25, 2004.
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