MySQL and BLOBs - Update File - We're Done!



We can update a column in much the same way that we write it, the only difference being that we specify a WHERE clause in our query that points to the record we wish to update.

rs.Open "Select * from files WHERE files.file_id = 1", conn, adOpenStatic, adLockOptimistic
mystream.Open
mystream.LoadFromFile "c:updateimage.gif"
rs!file = mystream.Read
rs.Update

mystream.Close
rs.Close

And that is it. Following is the complete samplecode.

Sample of using ADO Stream object to access BLOB data from a MySQL database.

'CREATE CONNECTION OBJECT AND ASSIGN CONNECTION STRING
Dim conn As ADODB.Connection
Set conn = New ADODB.Connection



conn.ConnectionString = "DRIVER={MySQL ODBC 3.51 Driver};" _
& "SERVER=127.0.0.1;" _
& "DATABASE=test;" _
& "UID=testuser;" _
& "PWD=12345;" _
& "OPTION=" & 1 + 2 + 8 + 32 + 2048 + 16384



conn.CursorLocation = adUseClient
conn.Open



'CREATE TABLE FOR SAMPLE CODE
conn.execute "CREATE TABLE files(" _
& "file_id SMALLINT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY, " _
& "file_name VARCHAR(64) NOT NULL, " _
& "file_size MEDIUMINT UNSIGNED NOT NULL, " _
& "file MEDIUMBLOB NOT NULL)"



'OPEN RECORDSET FOR WRITING
Dim rs As ADODB.Recordset
Set rs = New ADODB.Recordset



Dim mystream As ADODB.Stream
Set mystream = New ADODB.Stream



mystream.Type = adTypeBinary



rs.Open "SELECT * FROM files WHERE 1=0", conn, adOpenStatic, adLockOptimistic



rs.AddNew



mystream.Open
mystream.LoadFromFile "c:myimage.gif"



rs!file_name = "myimage.gif"
rs!file_size = mystream.size
rs!file = mystream.read
rs.Update
mystream.Close
rs.Close



'OPEN RECORDSET TO READ BLOB
rs.Open "Select * from files WHERE files.file_id = 1", conn
mystream.Open
mystream.Write rs!File
mystream.SaveToFile "c:newimage.gif", adSaveCreateOverWrite
mystream.close
rs.close



'OPEN RECORDSET FOR UPDATE OF BLOB COLUMN
rs.Open "Select * from files WHERE files.file_id = 1", conn, adOpenStatic, adLockOptimistic
mystream.Open
mystream.LoadFromFile "c:updateimage.gif"
rs!file = mystream.Read
rs.Update



mystream.Close
rs.Close



'OPEN RECORDSET TO READ UPDATED IMAGE
rs.Open "Select * from files WHERE files.file_id = 1", conn
mystream.Open
mystream.Write rs!file
mystream.SaveToFile "c:newupdatedimage.gif", adSaveCreateOverWrite



mystream.Close
rs.Close



conn.execute "DROP TABLE files"
conn.Close
msgbox "Success! Check your C: directory for newimage.gif and newupdatedimage.gif"




source :http://www.devarticles.com


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