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Tip of the Day
Language: Visual Basic
Expertise: Intermediate
Aug 21, 1997

Stored Access Queries Speed Response Time

In general, stored Access queries are faster than embedded SQL in your VB application. It can be a great benefit to be able to send parameters to the query directly from VB. Saving these queries in Access also reduces the amount of code you must maintain directly in your VB app. These code segments show how to send a parameter to a stored Access query. Here is the example Access SQL query:
 
PARAMETERS ID Text;
SELECT DISTINCTROW Host.IPAddress
FROM Host
WHERE Host.ID=[ID];
This code retrieves an IP address from an Access table, where the host ID in the table matches the host ID in the parameter. This code is stored in the Access database and has already been parsed and optimized. This is the key to gaining the performance benefits of stored queries. The Jet engine then uses this QueryDef when it is called from VB. Assume that there is a form with a data control on it. Here is the corresponding VB code to send the parameter:
 
Dim db As Database
Dim rs As Recordset
Dim qd As QueryDef
Set db = dthosts.Database
'dthosts is a data control on a form
Set qd = db.QueryDefs("aq_host")
'aq_host is the MS Access query name
qd.Parameters("ID") = "MY_Host_ID"
'host ID is the parameter for this query
Set rs = qd.OpenRecordset()
'open the recordset 
Set dthosts.Recordset = rs
'return the recordset to the data control
You can now use this data control in conjunction with a list-box control (or whatever control you like) to display the data. You can also add multiple parameters by adding more "qd.parameters" to the middle section of this code. Insert, update, and delete queries (or "action queries," as they are called in Access) can use parameters in the same fashion.
Al Gehrig,
 
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