I have an C++ application using MFC CRecordset to add rows to a table of an SQLite database, using the free ODBC driver by Ch. Werner. For this, I use the usual sequence of rs.Open(), rs.AddNew(), set values, and finally rs.Update().
This works on a small example, but with my actual database rs.Update() fails with error -1 and the following error message: unrecognized token: ""RedFaktorFly" (1). The 'token' is a truncated name of column 14 of the table, whose full name is "RedFaktorFlyt".
In some runs, it appends seemingly random characters, so the message becomes for ex. unrecognized token: ""RedFaktorFlyH" (1).
Interestingly, when I add "LongNames=true" to the ODBC connection string, which prepends table names to the column names and therefore makes the SQL query longer, the error becomes (for ex.) unrecognized token: ""K_Noder.MaxKompresjox" (1) - where "MaxKompresjonsFaktor" is the name of column 10 of the table.
This seems to suggest that there is a limit on the length of a SQL query accepted by the driver - but it seems strange that such a limit would be so small that it would fail already with 14 columns.
I do not think that the limit is in the C++ part, since the same code works fine both with the (commercial) SQLite driver from Devart and with Microsoft's ODBC driver for Access.
I tried adding a TraceFile option to the ODBC connection string, but it does not seem to do anything, so I do not know what exactly gets sent to the ODBC driver.
I see the same behaviour both with 32- and 64-bit builds, using Visual Studio 2015 on Windows 10.
Any suggestions what to try next?
I'll give you a solution to solve your issue completely. I don't know if it's suitable for you, but definitely it works. I successfully use it on my own.
For any operation except listing records, use CDatabase, not CRecordset. So, to insert rows to any table, to update records, to delete records, use CDatabase. To retrieve records from SQLLite database, use CRecordset. I can give you examples if you need.
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I am working on an application written in C++ that uses the 32-bit Instant Client drivers to access an Oracle database. The application uses the Record Field Exchange (RFX) methods to update the columns in the database tables. The database schema cannot be modified.
The C++ code was originally written to handle OID values as doubles because the OID column in the database is NUMBER(14), so a regular int won't be big enough. However, this leads to the database occasionally selecting a bad execution plan where it takes the OID values sent from the application and uses the to_binary_double function on them, rather than converting them to BIGINT. If this happens, the database does not do an index search over the data and instead does a full table scan.
We tried switching the OIDs to be type __int64 in the application, but there was an issue with the ODBC driver not supporting the BigInt type (or long long in C++). Similarly, when we tried to make the OIDs into longs, the database or the driver gave an error that the values sent to the database were too big for the column.
Working with the OIDs as Strings in C++ will work, but the database will never use the optimal index search because it has to convert the String to an integer before it can do any data retrieval. Because of this, we're just better off using the doubles we already have.
Does anyone have an idea of what we can do next? It is not the end of the world if we have to keep using doubles as before, but we were hoping to eliminate the chance for the database to run slowly.
We actually went with the "Convert all the OIDs to Strings in the C++ code" option. It turns out the database was still able to run an indexed search after converting the OIDs from Strings to integers. It would have been better if we switched ODBC driver to one that could handle BigInt, but that wasn't really an option for us so this will suffice.
I am currently developing server software in C++ with a MySQL data backend. I am using the official MySQL/connector library from Oracle to work with MySQL. The connection itself is working and I'm not having any issues with that.
My problem is that the database and the table schemas tend to change every once in a while because new tables and columns keep getting added. Also exiting column may be changed for the same reason. To make sure I recognize outdated server software quickly I wanted to add a warning when the database has changed.
My first idea was to hardcode how the database (and tables and such) should look and then check whether the current database matches the hardcoded data. But I have no clue how to achive that.
In summary I want to be able to detect whether
A table has been added or removed
A column in a table has been altered
A column in a table has been added or removed
with as little C++ code as possible. Also it should be quite easy to maintain.
Additional information will be added when required.
I would suggest the following approach:
1) fork and execute the mysql command line client. Set up a pair of pipes, to mysql's standard input and output.
2) At this point you should be able to execute simple commands by piping them to mysql via the standard input pipe, and read the output from the standard output pipe.
You will need to make careful notes as to the output format of each mysql command, so that you know when you finished reading its output, and you can send the next command.
3) As the first order of being, execute:
show tables;
The output that comes back will list all tables in the database. Parsing the output into a list of table names is trival. Then execute for each table:
show create table <tablename>;
The resulting output shows all fields in the table, its keys, and constraints. Pretty much all of this table's schema. Lather, rinse, repeat, for every table.
4) In this manner you can capture a basic schema of the entire database, for comparison purposes. If necessary, use the same approach to capture the triggers, and other objects. You'll likely need to do some minor massaging of the data, and exclude a few bits. "show create table", for example, will include the current AUTO_INCREMENT values, which you can ignore.
This general approach, of driving a mysql process via its standard input and output, is bit wobbly, of course. With a little bit of work, you can use mysql's native client library, and execute all of these commands, and capture their results, directly. This should be more reliable.
Background:
We have an application that uses the ODBC API to interact with Access and SQL Server (dynamically, depending on user's configuration).
I have discovered a bug which might be in the ODBC SQL driver, or may be a misconfiguration issue with the ODBC DSN we create, or may be a bug somehow in our code.
When a document is edited and saved, we query the database to see if this file has a corresponding record in the database - if so, we update the record with the updated data from the document; if not, we do an insert to create the necessary record for it.
We use the filename as the unique primary key on our table, and this works fine normally.
The bug is that if the filename contains characters outside of the current ANSI code page, then the select indicates no matches:
SQL: SELECT * FROM "My Designs" WHERE "PATHNAME" = '\\FILE-SERVER\Home Folders\User Files\狭すぎて丸め処理が出来ません!!.foo' [# matches = 0]
However, when the insert is attempted, we get a unique key violation (of course) - since there already is a record with that filename.
Database error: Violation of PRIMARY KEY constraint 'PK__My Desig__1B3D5B4BF643706B'. Cannot insert duplicate key in object 'dbo.My Designs'. The duplicate key value is (\\FILE-SERVER\Home Folders\User Files\狭すぎて丸め処理が出来ません!!.foo).
The statement has been terminated.
I've been over the code with a fine-tooth comb, and I can see nothing wrong. :(
The SQL statement that is being generated produces the correct Unicode output of the filename. Our application is compiled for Unicode. The column is SQL_WVARCHAR in ODBC speak.
I've tried adding AutoTranslate=no to the DSN configuration string, but that appears to have no effect.
I've tried logging the database connection from ODBC control panel. Sadly, that interface produces an ANSI log file - so I cannot verify UNICODE / ANSI issues using that tool.
Questions:
Is there a tool I can use to verify that these statements are being
created / issued correctly by the ODBC driver to the SQL Server
database?
Is there a better way to use ODBC so that the driver doesn't get canoodled by a simple UNICODE string in a SELECT query vs. an INSERT request?
Any other ideas for how to approach this problem (short of replacing our technology)
In the select statement, make sure you enclose the where clause string with a N to tell SQL it's unicode:
..."PATHNAME" = N'\\FILE-SERVER\Home Folders\User Files\狭すぎて丸め処理が出来ません!!.foo'
Also, MFC converts the data to MCBS or UNICODE depending on your configuration. Make sure you use CStringT in recordset.
I'm using a SQL Server CE database via Microsoft's OLEDB 3.5 SQL CE Driver. Here's my connection string:
Provider=Microsoft.SQLSERVER.CE.OLEDB.3.5;Data Source=C:\Users\me\Desktop\test1.sdf
This query works fine:
SELECT Thing FROM OtherThing WHERE name = 'TextThing'
This query fails:
SELECT Foo FROM Stuff
And this is the error I get:
Multiple-step operation generated errors. Check each status value.
The only structural difference in the table themselves is that one has a text primary key and the other has a bigint identity field as a primary key.
What I've tried:
http://support.microsoft.com/kb/269495 (neither of the resolution conditions are true for me)
Switched the cursorLocation property from adUseClient to adUseServer (this caused none of my queries to work - same error). That said, I think maybe I shouldn't give up on this one (thoughts?).
The problem has to do with the fact that the tables that caused that exception to be thrown were ones with fields of type nvarchar and sizes of 255. I changed those to ntext or reduced the size to 100 and no exception was thrown.
I'm using C++ and ADO to add data to a SQL Server 2005 database. When calling the Recordset Update method for a sql_variant column I'm getting the error DB_E_ERRORSOCCURRED and the error message Multiple-step OLE DB operation generated errors. Check each OLE DB status value, if available. No work was done. If the value I'm adding is NULL all works fine and all values going to the fields that are not sql_variant types work.
Does anyone know what I might be doing wrong?
Thanks
[Edit] I have some more information. The value we are storing is the empty string - ADO appears to want to store this in the sql_variant as a nchar(0), which of course is not a valid SQL data type. Is there a way to get an empty string in a sql_variant using the ADO batch commands?
You are only being shown the outer-most error there and as the error suggest you need to check the inner errors to find out the problem.
Apologies, I'm a VB developer but if you loop through the errors on your connection object you should be able to pinpoint the actual error.
From my classic ADO days multiple-step errors usually pointed at trying to stuff something to big into your column, e.g a string thats too big or a number with too high precision.
Hope this helps.
Ed