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How would you handle data type changes for an existing column?

SQLmedium0.8 min readPremium
Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Capco
Key Concepts Tested
window
Expert AnswerPremium
164 wordsInterview-ready
Handling data type changes for existing columns requires careful planning to avoid downtime and data loss. First, add a new column with the desired type alongside the existing one. Use CAST or CONVERT to populate it from the old column, handling edge cases (e.g., invalid dates, truncation). Validate the conversion with spot checks and row counts. Once validated, update downstream dependencies, then drop the old column and rename the new one....
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