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RAN-DBDEA-00219
Ranvier · DBDEA

Exam DBDEA Topics: transformation Difficulty: medium

A bronze table lands the amount column as STRING, with valid decimals like '125.50' and occasional junk like 'N/A'. The silver job must produce a DECIMAL(10,2) column, and every source row must survive: failed conversions should become NULL so the row can be routed to quarantine. Yesterday's run crashed with a CAST_INVALID_INPUT error on the first 'N/A' value. Which function meets the requirement?

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  1. A. try_cast(amount AS DECIMAL(10,2)) — it returns NULL for values it cannot convert, preserving the row for quarantine routing
  2. B. cast(amount AS DECIMAL(10,2)) — Spark substitutes a default 0 whenever the string is not a valid decimal number
  3. C. rlike() pre-validation — a regex can confirm the format but cannot produce the typed DECIMAL column the silver contract requires
  4. D. No change is needed — Spark's cast is already lenient and never raises an error when the input string is malformed
Reveal answer

Correct answer: try_cast(amount AS DECIMAL(10,2)) — it returns NULL for values it cannot convert, preserving the row for quarantine routing

Reference: https://docs.databricks.com/aws/en/sql/language-manual/sql-ref-functions

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Official Answer (A): try_cast(amount AS DECIMAL(10,2)) — it returns NULL for values it cannot convert, preserving the row for quarantine routing

Ranvier · DBDEA

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