Working with Different SQL Dialects Questions
Understand differences between SQL Server, PostgreSQL, BigQuery, Snowflake, and other databases. Know which functions are available in which databases (e.g., GENERATE_DATE_ARRAY in BigQuery vs. recursive CTEs in others) and how to adapt queries accordingly.
MediumTechnical
0 practiced
You need to search log messages for a complex regex such as an email or UUID pattern. Provide example queries using PostgreSQL (SIMILAR TO or ~), BigQuery (REGEXP_CONTAINS), and SQL Server (PATINDEX or CLR). Discuss performance considerations and options for indexing or precomputing regex matches.
HardSystem Design
0 practiced
Design an approach for handling slowly changing dimensions (SCD Type 2) for customers where updates arrive daily. Show how you would implement inserts and updates (preserve history) in BigQuery (MERGE into partitioned table), Snowflake (streams + tasks), and PostgreSQL (audit/history table or triggers). Address query patterns for current vs historical views.
HardSystem Design
0 practiced
You're responsible for migrating 10TB of reporting data and 2,000 stored procedures from on-prem SQL Server to BigQuery to reduce operational overhead. Draft a high-level migration plan that covers function and feature mapping, stored procedure replacement (e.g., scheduling, scripting), query translation, testing, security, performance tuning, and cost estimation.
HardTechnical
0 practiced
A BI dashboard intermittently shows different top-products each refresh. The underlying SQL uses GROUP BY product, ORDER BY SUM(sales) DESC without a deterministic tiebreaker. Explain why results can be nondeterministic across database engines and propose robust fixes. Consider differences in planner optimizations and parallel execution across Postgres, BigQuery, and Snowflake.
MediumTechnical
0 practiced
Create a report that pivots monthly revenue by product for the last 3 months. Show how to implement this pivot in: 1) SQL Server using PIVOT; 2) PostgreSQL using crosstab (tablefunc) or conditional aggregation; 3) BigQuery using conditional aggregation. Also outline how to handle a dynamic number of months in each dialect.
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