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ODBC - Open DataBase Connectivity
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Basic Steps
Connecting to the SQL Server DataBase for retrieving information from tables
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The steps 1 - 3 are for connecting to the SQL Server Database
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1. Allocate ODBC Environment Handle
If SQLAllocEnv(glEnv) <> 0 Then
MsgBox "Unable to initialize ODBC API drivers!"
End
End If
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2. Allocate ODBC Database Handle
Dim iStatus As Integer
If SQLAllocConnect(glEnv, glDbc) <> 0 Then
MsgBox "Could not allocate memory for connection Handle!"
ODBCInit = False
' Free the Environment
iStatus = SQLFreeEnv(lEnv)
If iStatus = SQL_ERROR Then
MsgBox "Error Freeing Environment From ODBC Drivers"
End If
' Quit the Application
End
End If
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3. Connect using the sConnect string - SQLDriverConnect
Dim sResult As String
Dim iSize As Integer
Dim sConnect As String
sConnect = "DSN=" & gsDSN & ";UID=" & gsLoginID & ";PWD=" & gsPassword & ";APP=" & gsAppCode & ";DATABASE=" & gsDatabase
If SQLDriverConnect(glDbc, Screen.ActiveForm.hWnd, sConnect, Len(sConnect), sResult, Len(sResult), iSize, 0) <= 0 Then
MsgBox "Could not establish connection to ODBC driver!"
End If
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The steps 4 - 8 are for retrieving data from tables
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4. Allocate ODBC Statement Handle
If SQLAllocStmt(glDbc, glStmt) <> 0 Then
MsgBox "Could not allocate memory for a statement handle!"
End If
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5. Execute ODBC Statement - SQLExecDirect
Dim lRet As Long, lErrNo As Long
Dim iLen As Integer
Dim sSQLState As String * MAX_DATA_BUFFER
Dim sErrorMsg As String * MAX_DATA_BUFFER
Dim sMsg As String
sSQL = "SELECT name, location FROM authors"
If SQLExecDirect(glStmt, sSQL, Len(sSQL)) <> SQL_SUCCESS Then
' Also Check for ODBC Error message - SQLError
lRet = SQLError(glEnv, gldbc, glStmt, sSQLState, lErrNo, sErrorMsg, MAX_DATA_BUFFER, iLen)
sMsg = "Error Executing SQL Statement" & Chr$(13) & Chr$(10)
sMsg = sMsg & "ODBC State = " & Trim$(Left$(sSQLState, InStr(sSQLState, Chr$(0)) - 1)) & Chr$(13) & Chr$(10)
sMsg = sMsg & "ODBC Error Message = " & Left$(sErrorMsg, iLen)
MsgBox sMsg, vbInformation, "Execute Query"
End If
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6. Fetch one row of results from executed ODBC Statement - SQLFetch
Code in Step 7.
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7. Get the Data in each field of the Fetched row - SQLGetData
Dim bPerform As Integer, iStatus As Integer
Dim sData As String * MAX_DATA_BUFFER
Dim lOutLen As Long
bPerform = SQLFetch(glStmt)
Do While bPerform
bPerform = SQLFetch(lStmt) ' Get the next row of data
If bPerform = SQL_SUCCESS Then ‘ If rows of data available
bPerform = True
' Get Author Name - iColumn = 1 for first field i.e. name in sSQL
iStatus = SQLGetData(glStmt, iColumn, 1, sData, MAX_DATA_BUFFER, lOutLen)
' lOutlen = length of the valid data in sData
' Data value will be = Left$(sData, lOutlen), lOutlen = -1 if no data or Null data
' Get Location - iColumn = 2 for second field i.e. location in sSQL
iStatus = SQLGetData(glStmt, iColumn, 1, sData, MAX_DATA_BUFFER, lOutLen)
' Add the Field Data to Correponding Data Display Controls for this row
Else
bPerform = False ' No more rows available
End If
Loop
'Release the ODBC Statement Handle
bPerform = SQLFreeStmt(glStmt, SQL_DROP)
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8. Release the ODBC Statement Handle - SQLFreeSTmt
Code in Step 7.
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The steps 9 - 11 are for Disconnecting from the SQL Server DataBase
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9. Disconnect from ODBC Database - SQLDisconnect
iStatus = SQLDisconnect(glDbc)
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10. Release the ODBC Database Handle - SQLFreeConnect
iStatus = SQLFreeConnect(glDbc)
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11. Release the ODBC Environment Handle - SQLFreeEnv
iStatus = SQLFreeEnv(glEnv)
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The following entries are required in the ODBCAPI module
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' ODBC Variables and Constants
Global glEnv As Long
Global glDbc As Long
Global sSQL As String
Global Const MAX_DATA_BUFFER = 255
Global Const SQL_SUCCESS = 0
Global Const SQL_SUCCESS_WITH_INFO = 1
Global Const SQL_ERROR = -1
Global Const SQL_NO_DATA_FOUND = 100
Global Const SQL_CLOSE = 0
Global Const SQL_DROP = 1
Global Const SQL_CHAR = 1
Global Const SQL_NUMERIC = 2
Global Const SQL_DECIMAL = 3
Global Const SQL_INTEGER = 4
Global Const SQL_SMALLINT = 5
Global Const SQL_FLOAT = 6
Global Const SQL_REAL = 7
Global Const SQL_DOUBLE = 8
Global Const SQL_VARCHAR = 12
Global Const SQL_DATA_SOURCE_NAME = 6
Global Const SQL_USER_NAME = 8
'ODBC Declarations
'The hWnd is a Long in Windows 95 & Windows NT
#If Win32 Then
Declare Function SQLAllocEnv Lib "odbc32.dll" (env As Long) As Integer
Declare Function SQLFreeEnv Lib "odbc32.dll" (ByVal env As Long) As Integer
Declare Function SQLAllocConnect Lib "odbc32.dll" (ByVal env As Long, ldbc As Long) As Integer
Declare Function SQLConnect Lib "odbc32.dll" (ByVal ldbc As Long, ByVal Server As String,ByVal serverlen As Integer, ByVal uid As String, ByVal uidlen As Integer, ByVal pwd As String, ByVal pwdlen As Integer) As Integer
Declare Function SQLDriverConnect Lib "odbc32.dll" (ByVal ldbc As Long, ByVal hWnd As Long, ByVal szCSIn As String, ByVal cbCSIn As Integer,ByVal szCSOut As String, ByVal cbCSMax As Integer, cbCSOut As Integer, ByVal f As Integer) As Integer
Declare Function SQLFreeConnect Lib "odbc32.dll" (ByVal ldbc As Long) As Integer
Declare Function SQLDisconnect Lib "odbc32.dll" (ByVal ldbc As Long) As Integer
Declare Function SQLAllocStmt Lib "odbc32.dll" (ByVal ldbc As Long, lStmt As Long) As Integer
Declare Function SQLFreeStmt Lib "odbc32.dll" (ByVal lStmt As Long, ByVal EndOption As Integer) As Integer
Declare Function SQLTables Lib "odbc32.dll" (ByVal lStmt As Long, ByVal q As Long, ByVal cbq As Integer, ByVal o As Long, ByVal cbo As Integer, ByVal t As Long, ByVal cbt As Integer, ByVal tt As Long, ByVal cbtt As Integer) As Integer
Declare Function SQLExecDirect Lib "odbc32.dll" (ByVal lStmt As Long, ByVal sqlString As String, ByVal sqlstrlen As Long) As Integer
Declare Function SQLNumResultCols Lib "odbc32.dll" (ByVal lStmt As Long, NumCols As Integer) As Integer
Declare Function SQLDescribeCol Lib "odbc32.dll" (ByVal lStmt As Long, ByVal colnum As Integer, ByVal colname As String, ByVal Buflen As Integer, colnamelen As Integer, dtype As Integer, dl As Long, ds As Integer, n As Integer) As Integer
Declare Function SQLFetch Lib "odbc32.dll" (ByVal lStmt As Long) As Integer
Declare Function SQLGetData Lib "odbc32.dll" (ByVal lStmt As Long, ByVal col As Integer, ByVal wConvType As Integer, ByVal lpbBuf As String, ByVal dwbuflen As Long, lpcbout As Long) As Integer
Declare Function SQLGetInfo Lib "odbc32.dll" (ByVal ldbc As Long, ByVal hWnd As Long, ByVal szInfo As String, ByVal cbInfoMax As Integer, cbInfoOut As Integer) As Integer
Declare Function SQLError Lib "odbc32.dll" (ByVal env As Long, ByVal ldbc As Long, ByVal lStmt As Long, ByVal SQLState As String, NativeError As Long, ByVal Buffer As String, ByVal Buflen As Integer, Outlen As Integer) As Integer
#Else
Declare Function SQLAllocEnv Lib "odbc.dll" (env As Long) As Integer
Declare Function SQLFreeEnv Lib "odbc.dll" (ByVal env As Long) As Integer
Declare Function SQLAllocConnect Lib "odbc.dll" (ByVal env As Long, ldbc As Long) As Integer
Declare Function SQLConnect Lib "odbc.dll" (ByVal ldbc As Long, ByVal Server As String, ByVal serverlen As Integer, ByVal uid As String, ByVal uidlen As Integer, ByVal pwd As String, ByVal pwdlen As Integer) As Integer
Declare Function SQLDriverConnect Lib "odbc.dll" (ByVal ldbc As Long, ByVal hWnd As Integer, ByVal szCSIn As String, ByVal cbCSIn As Integer, ByVal szCSOut As String, ByVal cbCSMax As Integer, cbCSOut As Integer, ByVal f As Integer) As Integer
Declare Function SQLFreeConnect Lib "odbc.dll" (ByVal ldbc As Long) As Integer
Declare Function SQLDisconnect Lib "odbc.dll" (ByVal ldbc As Long) As Integer
Declare Function SQLAllocStmt Lib "odbc.dll" (ByVal ldbc As Long, lStmt As Long) As Integer
Declare Function SQLFreeStmt Lib "odbc.dll" (ByVal lStmt As Long, ByVal EndOption As Integer) As Integer
Declare Function SQLTables Lib "odbc.dll" (ByVal lStmt As Long, ByVal q As Long, ByVal cbq As Integer, ByVal o As Long, ByVal cbo As Integer, ByVal t As Long, ByVal cbt As Integer, ByVal tt As Long, ByVal cbtt As Integer) As Integer
Declare Function SQLExecDirect Lib "odbc.dll" (ByVal lStmt As Long, ByVal sqlString As String, ByVal sqlstrlen As Long) As Integer
Declare Function SQLNumResultCols Lib "odbc.dll" (ByVal lStmt As Long, NumCols As Integer) As Integer
Declare Function SQLDescribeCol Lib "odbc.dll" (ByVal lStmt As Long, ByVal colnum As Integer, ByVal colname As String, ByVal Buflen As Integer, colnamelen As Integer, dtype As Integer, dl As Long, ds As Integer, n As Integer) As Integer
Declare Function SQLFetch Lib "odbc.dll" (ByVal lStmt As Long) As Integer
Declare Function SQLGetData Lib "odbc.dll" (ByVal lStmt As Long, ByVal col As Integer, ByVal wConvType As Integer, ByVal lpbBuf As String, ByVal dwbuflen As Long, lpcbout As Long) As Integer
Declare Function SQLGetInfo Lib "odbc.dll" (ByVal ldbc As Long, ByVal hWnd As Integer, ByVal szInfo As String, ByVal cbInfoMax As Integer,cbInfoOut As Integer) As Integer
Declare Function SQLError Lib "odbc.dll" (ByVal env As Long, ByVal ldbc As Long, ByVal lStmt As Long, ByVal SQLState As String, NativeError As Long, ByVal Buffer As String, ByVal Buflen As Integer, Outlen As Integer) As Integer
#End If 
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