Tag Archives: mySQL

Odbc Memory allocation error

Today I tried upgrading the odbc drivers on my server from 3.5 to 5.1. I immediately ran in to troubles and got a “Memory allocation error” when executing a non query to mySql. After reverting back to driver version 3.5 i found that the error was caused simply by a “data too long for field” error which i quickly fixed in no time at all.

I am not sure if the memory allocation error i received with the new drivers was related to this but if anyone could explain this I would love to know whats going off. If anyone gets a memory allocation error in 5.1 it might be worth checking to ensure the data your inserting fits into the row.

Connection string rules

Important rules for connection strings

This is general rules adopted by most drivers and providers. However, keep in mind that these rules is not 100% accurate for every driver and every situation.

Never the less, following and knowing about these basic rules will keep some common problems out of your way. Okay? Here we go..
  • All blank characters, except those placed within a value or within quotation marks, are ignored
  • Blank characters will though affect connection pooling mechanism, pooled connections must have the EXACT same connection string
  • If a semicolon (;) is part of a value it must be delimited by quotation marks (“)
  • Use a single-quote (‘) if the value begins with a double-quote (“)
  • Conversely, use the double quote (“) if the value begins with a single quote (‘)
  • No escape sequences are supported
  • The value type is NOT relevant
  • Names are case iNsEnSiTiVe
  • If a KEYWORD=VALUE pair occurs more than once in the connection string, the value associated with the LAST occurrence is used
  • But!… if the PROVIDER keyword occurs multiple times in the string, the FIRST occurrence is used.
  • If a keyword contains an equal sign (=), it must be preceded by an additional equal sign to indicate that it is part of the keyword.

Avioding SQL injection

After much playing around and problems I finally figured how to add safe parameters into an odbc command. Here is a sample….

OdbcCommand postcomment = new OdbcCommand(“insert into comments values (‘”+newguid+”‘,’”+itemid+”‘,?)”, temp);

Here the ? represents the first and only parameter to be passed into the command using..

postcomment.Parameters.AddWithValue(“@comment”, comment);

then

postcomment.ExecuteNonQuery();

If you were to include > 1 ? symbols, the parameters must be added in the order they appear in your original command.