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Count the number of nulls in each column of a table.

SQLeasy0.5 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
Incedo
Key Concepts Tested
bigquerysparksql
Expert AnswerPremium
90 wordsInterview-ready
**Architectural Logic**: Null counting is a data quality primitive; automation scales governance. **SQL**: `SELECT SUM(CASE WHEN col1 IS NULL THEN 1 ELSE 0 END) AS col1_nulls, ... FROM table`. Or `COUNT(*) - COUNT(col1)` (when NULL excluded from COUNT). **BigQuery**: `COUNTIF(col1 IS NULL)`. **Spark**: `df.agg(*[sum(when(col(c).isNull(), 1).otherwise(0)).alias(c) for c in df.columns])`. **Why Automate**: For 50+ columns, dynamic SQL or schema iteration; run as part of CI/data quality framework....
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