"String Data, Length Mismatch" Error Message with ODBC Driver for SQL Server If Application Inserts More Than 400 KB of Text Data

If an application inserts more than 400 kilobytes (KB) of data in SQL Server by using ODBC, you may receive the following error message: You receive this error message if the application uses the ODBC application programming interface (API) directly (that is, the SQLBindParameter, the SQLParamData, the SQLExecute, and the SQLPutData APIs). Additionally, you receive this error message if you try to insert data through a Microsoft Access linked table to SQL Server, and if all of the following conditions are true:

• The application inserts more than 400 KB of data.
• The application calls SQLBindParameter with SQL_C_WCHAR and SQL_LONGVARCHAR. If the application links with Access, Access calls SQLBindParameter with SQL_C_WCHAR and SQL_LONGVARCHAR.
• The server data type is non-Unicode such as "text." Internally, this causes the SQL Server driver to convert the data that you have passed from Unicode to MultiByte.
• The application uses the SQL_LEN_DATA_AT_EXEC(409602) macro to indicate that you are trying to send more than 400 kilobytes of data. If you are using Access, Access uses this macro automatically.

This problem occurs with the ODBC Driver for SQL Server that is included with Microsoft Data Access Components (MDAC) versions 2.5, 2.6, and 2.7.

Based on the ODBC specification, when a client calls SQL_LEN_DATA_AT_EXEC and passes a number as its parameter, such as SQL_LEN_DATA_AT_EXEC(409602), the number that is passed indicates how many bytes of data is sent when the client calls SQLPutData later. This problem occurs because the ODBC Driver for SQL Server incorrectly interprets this number as the number of characters that are passed instead of number of bytes that are passed.

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Microsoft Data Access Components service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The typical support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

To work around this problem, bind the parameter as SQL_C_CHAR (instead of as SQL_C_WCHAR), and then pass non-Unicode data.

If you are using an Access linked table to update your SQL Server table, you cannot use this workaround because Access always binds text parameters as SQL_C_WCHAR.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

Steps to Reproduce the Problem

1. Create the following tables in SQL Server:

   if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[repro]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
   drop table [dbo].[repro]
   GO
   
   CREATE TABLE [dbo].[repro] (
   	[name] [text] COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
   	[id] [char] (10) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL 
   ) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
   GO
   
   ALTER TABLE [dbo].[repro] WITH NOCHECK ADD 
   	CONSTRAINT [PK_repro] PRIMARY KEY  CLUSTERED 
   	(
   		[id]
   	)  ON [PRIMARY] 
   GO
   
   Insert Into Repro (name,id) Values ('abc','1234')
   					

2. Use the following code to reproduce the problem:

   #include "stdafx.h"
   #include <stdio.h>
   #include <iostream.h>
   #include <windows.h>
   #include <sql.h>
   #include <sqlext.h>
   #include <sqltypes.h>
   
   
   void HandleError(SQLHANDLE	hHandle, SQLSMALLINT hType, RETCODE RetCode)
   {
   	SQLSMALLINT	iRec = 0;
   	SQLINTEGER	iError;
   	TCHAR		szMessage[1000];
   	TCHAR		szState[SQL_SQLSTATE_SIZE];
   
   
   	if (RetCode == SQL_INVALID_HANDLE)
   	{
   		fprintf(stderr,"Invalid handle!\n");
   		return;
   	}
   
   
   	while (SQLGetDiagRec(hType,
   			     hHandle,
   			     ++iRec,
   			     (SQLCHAR *)szState,
   			     &iError,
   			     (SQLCHAR *)szMessage,
   			     (SQLSMALLINT)(sizeof(szMessage) / 
   			     sizeof(TCHAR)),
   			     (SQLSMALLINT *)NULL) == SQL_SUCCESS)
   	{
   	fprintf(stderr,TEXT("[%5.5s] %s (%d)\n"),szState,szMessage,iError);
   	}
   
   }
   
   
   class ODBC_Class
   {
   	//attributes
   	public:
   	SQLHANDLE	henv;
   	SQLHANDLE	hdbc1;
   	SQLHANDLE	hstmt;
   	SQLRETURN	rc;
   
   
   	//methods
   	public:
   	ODBC_Class();
   	~ODBC_Class();
   	SQLRETURN	SendLongData();
   };
   
   
   ODBC_Class::ODBC_Class()
   {
     rc = SQL_SUCCESS;	//init the return code variable
   
     //Allocate an environment handle.
     rc = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &henv);	//Allocate the env handle.
   
     //Set the ODBC application version to 3.x.
     if (rc ==SQL_SUCCESS)
   	rc = SQLSetEnvAttr(henv,SQL_ATTR_ODBC_VERSION, (SQLPOINTER)
                               SQL_OV_ODBC3, SQL_IS_UINTEGER);
   
     //Allocate a connection handle.
     if (rc == SQL_SUCCESS)
        rc = SQLAllocHandle(SQL_HANDLE_DBC,henv, &hdbc1);	
   }
   
   
   ODBC_Class::~ODBC_Class()
   {
   //Free the connection handle.
   if (hdbc1 != NULL)
   	SQLFreeHandle(SQL_HANDLE_DBC, hdbc1);
   
   //Free the environment handle.
   if (henv != NULL)
   	SQLFreeHandle(SQL_HANDLE_ENV, henv);
   }
   
   
   
   
   int main(int argc, char* argv[])
   {
   
   	SQLRETURN	rc		= SQL_SUCCESS;
   	CHAR		DBName[100]	= "YourDataBaseName";
   	CHAR		User[100]	= "YourUID";
   	CHAR		Password[100]	= "YourPassword";
   
   	CHAR		SQLstmt[255];
   	CHAR*		m_id		= ("1234");
   	CHAR*		m_name;
   	OLECHAR*	pSrc;
   	SQLINTEGER	bufsize		= 204801;
   	SQLINTEGER	ValSizeName = 5;
   	SQLINTEGER	ValSizeID   = SQL_DATA_AT_EXEC;
   	SQLINTEGER	paramMarker = 1;
   	
   
   	ODBC_Class Example; //Create an instance of the ODBC_Class to use.
   
   	if (Example.hdbc1 != NULL)
   	{
   	//Connect to the database.
   	  rc = SQLConnect(Example.hdbc1, (SQLCHAR*) DBName, SQL_NTS,
                                 (SQLCHAR*)User, SQL_NTS, (SQLCHAR*) Password,
                                 SQL_NTS);
   	  if (rc == SQL_SUCCESS || rc == SQL_SUCCESS_WITH_INFO)
   		cout << "Connected to " << DBName<< " \n\n" << endl;
   		
   
   	  //Allocate stmt handle.
   	  rc = SQLAllocStmt(Example.hdbc1, &Example.hstmt);	
   	  if ( rc == SQL_SUCCESS)
   	  {
   		UINT	info2 = 60;	//Set the timeout value in seconds.
   			
   		//Fill in the data "abcd...."
   		m_name = new char[bufsize];
   		for (int i = 0; i < bufsize; i++)
   		m_name[i] = (i % 26) + 65;
   
   		m_name[bufsize-1] = '#';
   		OLECHAR* m_olechar = new OLECHAR[bufsize*2];
   
   		int result = MultiByteToWideChar(CP_ACP, 0, m_name, -1,
                                                     m_olechar, bufsize*2);
   
   		//Bind the parameters.
   			
   		rc = SQLBindParameter(Example.hstmt,1,SQL_PARAM_INPUT,		
   	                             SQL_C_WCHAR, SQL_LONGVARCHAR,
                                        bufsize*2, 0, (SQLPOINTER)
                                        paramMarker, 0, &ValSizeName); 
   
   		if (rc != SQL_SUCCESS)
   		{
   		  HandleError(Example.hstmt,SQL_HANDLE_STMT, rc);
   		}
   	
   		rc = SQLBindParameter(Example.hstmt,2,SQL_PARAM_INPUT,
   		SQL_C_DEFAULT, SQL_CHAR, 4, 0, (SQLPOINTER) m_id, 4, NULL); 
   
   		strcpy(SQLstmt,"UPDATE repro SET name=? WHERE id=?");
   
   		ValSizeName = SQL_LEN_DATA_AT_EXEC(bufsize*2);
   		rc = SQLExecDirect(Example.hstmt, (SQLCHAR*) SQLstmt, 
                                      SQL_NTS);			
   		paramMarker = -1;
   		rc = SQLParamData(Example.hstmt, 
                                      (SQLPOINTER*)&paramMarker);
   
   		//Loop through and insert the data.
   		int j = 2*bufsize/8188;
   		int remains = bufsize*2;		
   		pSrc = m_olechar;			
   		for (int k=0; k<j; k++)
   		{
   		  remains -= 8188;
   		  rc =SQLPutData(Example.hstmt,(SQLPOINTER)pSrc , 8188);
   		  if (rc != SQL_SUCCESS)
                      HandleError(Example.hstmt,SQL_HANDLE_STMT, rc);
   		  pSrc += 4094; //Increment widechar pointer by 4094 = 8188 
                                   //bytes
   		  cout << rc << "\n";
   
   		}
   		rc =SQLPutData(Example.hstmt,(SQLPOINTER)pSrc , remains);
   
   		rc = SQLParamData(Example.hstmt, (SQLPOINTER*)paramMarker); 
   		if (rc != SQL_SUCCESS)
   		  HandleError(Example.hstmt, SQL_HANDLE_STMT, rc);
   		}
   		rc = SQLDisconnect(Example.hdbc1);
   	}
   	return (rc);
   }
   						

   NOTE: Change the connection string as appropriate for your environment.