An Adobe Commerce developer is trying to create a custom table using declarative schema, but is unable to do so. What are two errors in the snippet above? (Choose two.)

Question

Exhibit

Options

• AColumn (roll_no) does not have index. It is needed since attribute identity is set to true.
• BColumn (entity_id) does not have index. It is needed since attribute identity is set to false.
• CColumn (student_name) does not have attribute length.
• Dnull is not a valid value for column (roll_no).

Explanation

The correct answers are A and C.

Why A is correct: In Adobe Commerce declarative schema (db_schema.xml), a column with identity="true" is an auto-increment column and must be defined as a primary key with a corresponding <constraint> element of type PRIMARY. Without that index/constraint, the schema processor cannot validate or apply the table definition, causing a setup error.

Why C is correct: String-type columns (e.g., varchar) in declarative schema require an explicit length attribute. Omitting it is a syntax/validation error because Magento cannot determine the column's storage size - there is no default fallback for string length in db_schema.xml.

Why B is wrong: identity="false" simply means the column is not auto-increment. That condition alone does not mandate an index; indexes are only required for specific use cases like primary keys or foreign key targets.

Why D is wrong: null (i.e., nullable="true") is a perfectly valid attribute value in declarative schema. Whether a column accepts NULL values is controlled by the nullable attribute and is not inherently an error.

Memory tip: Think "Auto-increment = needs a primary key" (A) and "String = needs a size" (C) - both are cases where the schema engine needs explicit information it cannot guess on its own.

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