How to resolve errors when declaring variables in MySQL?

The syntax for declaring variables in MySQL is to use the SET keyword to assign a value to the variable. If an error occurs while declaring a variable, it could be due to the following reasons:

1. Syntax error: please verify that the variable declaration is correct. Variable names should start with the “@” symbol, for example “@myVariable”.
2. Assign 10 to the variable myVariable.
3. Repeated variable names: Make sure that variable names are not declared more than once. If variables are declared more than once within the same scope, it will result in an error.
   Example of error:
4. Set @myVariable to 10;
   Set @myVariable to 20; — Error, variable redeclaration
5. Scope error: Please check if the variable’s scope is correct. The scope of a variable is only valid within the query where it was declared and is not valid in other queries. Using a variable after it has been declared in a query will result in an error.
   Example of error:
6. Set the variable @myVariable to 10.

   Display the value of @myVariable within the same query.

   Retrieve all records from myTable where the column value matches @myVariable, which is incorrect because the variable is out of scope.

If the above methods still cannot solve the problem, please provide more specific error information and code examples so that we can better help you resolve the issue.