Can .NET MySqlCommand Use MySQL User-Defined Variables?

Can .NET MySqlCommand Leverage MySQL User Defined Variables?

Executing a MySQL query in .NET using MySqlAdapter can pose challenges if the query utilizes user defined variables.

Specific Query Attempt:

The following SQL statement attempts to assign row numbers to distinct rows:

SELECT @rownum := @rownum +1 rownum, t . *
FROM (
  SELECT @rownum :=0
) r, (
  SELECT DISTINCT
    TYPE FROM `node`
  WHERE TYPE NOT IN ('ad', 'chatroom')
)t     

Exception Encountered:

When this query is executed in .NET, an exception occurs because the @rownum variable is interpreted as a parameter, which requires explicit definition.

Solution:

To resolve this issue, it is necessary to specify that user variables are allowed in the connection string. This can be achieved by adding the following parameter:

;Allow User Variables=True

Updated Connection String:

sqlConnection.ConnectionString = "Data Source=localhost;Initial Catalog=myDb;Username=myUser;Password=myPwd;Allow User Variables=True";

Additional Information:

This solution is compatible with newer versions of the .NET Connector for MySQL. For more details, refer to this blog: [How to Use User Defined Variables in .NET with MySQL](linked blog).

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