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Maintaining and Automating Data Workloads →mediumMultiple SelectObjective-mapped

PDE Maintaining and Automating Data Workloads Practice Question

A data engineer needs to migrate a schema from BigQuery where a column is currently REQUIRED and needs to become NULLABLE. Which TWO statements are correct? (Choose 2)

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

Drop the column and add it again as NULLABLE

BigQuery does not allow changing a column from REQUIRED to NULLABLE directly. One must either drop and recreate the column or use a query to create a new table.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✗

    Use ALTER TABLE RENAME COLUMN and then add new column

    Why it's wrong here

    Renaming does not change mode.

  • ✓

    Drop the column and add it again as NULLABLE

    Why this is correct

    Dropping and adding the column changes its mode to NULLABLE.

  • ✗

    Use bq update --schema to change the mode

    Why it's wrong here

    bq update does not support changing column mode directly.

  • ✓

    Create a new table with the desired schema and use a query to populate it

    Why this is correct

    This is a common workaround: create new table with NULLABLE, then INSERT SELECT.

  • ✗

    Use ALTER TABLE ALTER COLUMN SET DATA TYPE to change to NULLABLE

    Why it's wrong here

    ALTER COLUMN only allows relaxing a column from REQUIRED to NULLABLE if using DDL with SET NOT NULL? Actually BigQuery only allows relaxing REQUIRED to NULLABLE via SQL using a query or manually recreating the table.

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Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This PDE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PDE exam.