<|im_start|>system
You are a helpful AI assistant.<|im_end|>
<|im_start|>user
I have this SQL error, what's the problem? : AN SQLSTATE OR SQLCODE VARIABLE DECLARATION IS IN A NESTED COMPOUND STATEMENT<|im_end|>
<|im_start|>assistant
The error message "An SQLSTATE or SQLCODE variable declaration is in a nested compound statement" usually indicates that you have declared an SQLSTATE or SQLCODE variable within a compound statement (BEGIN ... END). In most databases, this is not allowed and the variable must be declared in the outermost scope.

To resolve this error, you need to move the declaration of the SQLSTATE or SQLCODE variable to the outermost scope and ensure that it is not within any compound statements.

Here's an example to illustrate this:

-- Incorrect: Declaration within a compound statement
DO
BEGIN
    DECLARE @sqlstate VARCHAR(5);
    -- more code here
END;

-- Correct: Declaration in the outermost scope
DECLARE @sqlstate VARCHAR(5);
DO
    -- more code here
END;<|im_end|>
<|im_start|>user
What are common causes of that error? How can I fix it?<|im_end|>
<|im_start|>assistant
Common causes of the error "AN SQLSTATE OR SQLCODE VARIABLE DECLARATION IS IN A NESTED COMPOUND STATEMENT" include:

Improper use of SQLSTATE or SQLCODE variables: If the SQLSTATE or SQLCODE variables are declared within a nested block of code, the error will occur.

Misunderstanding of the purpose of SQLSTATE and SQLCODE: Some developers may mistakenly believe that SQLSTATE and SQLCODE are just normal variables, when in fact they are used specifically to track the success or failure of SQL operations.

Cut and paste coding errors: If a developer has copied code from one part of the program to another without understanding its purpose, they may accidentally introduce the error into the code.

To fix the error, you should ensure that the SQLSTATE and SQLCODE variables are declared at the highest level of the code, outside of any nested blocks. This will allow them to accurately track the success or failure of SQL operations throughout the entire program. If the variables are being used within a nested block for some other purpose, you should either remove the declaration from the nested block, or find an alternative solution that does not rely on SQLSTATE or SQLCODE variables.<|im_end|>