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What is UNNEST and provide a query example?

SQLmedium0.5 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
EY
Key Concepts Tested
bigqueryjoinsql
Expert AnswerPremium
106 wordsInterview-ready
UNNEST converts an array into a set of rows. In BigQuery: SELECT id, item FROM my_table, UNNEST(items_array) AS item. Example: WITH data AS (SELECT 1 id, [1,2,3] arr) SELECT id, x FROM data, UNNEST(arr) AS x; -- returns 3 rows. Use for: exploding arrays for analysis, joining array elements. In PostgreSQL: unnest(arr). Best practice: Use with CROSS JOIN or comma for 1:1; LATERAL for correlated. Handle NULL arrays—use COALESCE or IFNULL to provide empty array....
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