• The error 'Scalar subquery might produce more than one row' occurs when a scalar subquery in the SQL query returns multiple rows instead of a single value.

• To resolve this issue, you can use the 'LIMIT 1' clause in your subquery to ensure that only one row is returned.

• Here is an example of how you can modify your SQL query to avoid the error:

CREATE TABLE demo1 (name string, PRIMARY KEY (name));
INSERT INTO demo1(name) VALUES ('demoname');
SELECT SUBSTR((SELECT name FROM demo1 LIMIT 1), 2);

By adding 'LIMIT 1' to your subquery, you can ensure that it returns only one row and resolves the error.