The following reasons are possible:
1. In a CREATE VIEW statement, the number of view table columns to be defined must be equal to the number of columns issued as the result of the QUERY expression. In the present case, the number of columns in the QUERY request result exceeds the number of defined view table columns.
2. The number of subquery output columns specified in a SET UPDATE clause must be precisely one. In some SQL modes, this restriction also applies in the comparison predicate, quantity comparison predicate and IN predicate. In the present case, the subquery produced more than one output column.
3. An SQL statement was specified for data retrieval. The number of output columns must be less than or equal to 254. This number was exceeded.
4. Increase the number of view table columns specified in the CREATE VIEW statement, or reduce the number of output columns of the QUERY expression.
5. Limit the number of subquery output columns to one.
6. Correct the data query statement by removing one or more output columns.