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Concatenate Columns in PySpark

Spark/Big Dataeasy0.4 min readPremium
Frequency
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Asked at 1 company
Category
452
questions in Spark/Big Data
Difficulty Split
88E|81M|283H
in this category
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1,863
across 7 categories
Asked at these companies
Presidio
Key Concepts Tested
spark
Expert AnswerPremium
72 wordsInterview-ready
**Methods**: `concat(col1, col2)` or `concat_ws(sep, col1, col2)`. `concat_ws` skips nulls; `concat` with null yields null. For mixed types, cast first. **Example**: `df.withColumn("full_name", concat_ws(" ", col("first_name"), col("last_name")))`. **Why it matters**: String ops can be expensive at scale; built-ins are optimized. **Scalability trade-offs**: Row-wise UDF for concat = slow; use built-in. **Cost implications**: Trivial for small tables; for large, avoid UDF....
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