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23. Data quality checks

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- Databases
  Databases
  - SQL
    
    SQL
    
    SQL interview fast track
    
    SQL cheat sheet
    
    The sample database: a small shop
    
    1. Tables, rows and keys
    
    2. SELECT, WHERE, ORDER BY, LIMIT
    
    3. The order a query really runs in
    
    4. Expressions: CASE, numbers, dates, CAST
    
    5. Text functions and pattern matching
    
    6. NULL and three-valued logic
    
    7. Aggregation: GROUP BY and HAVING
    
    8. Joins: inner, left, right, full, cross
    
    9. Self, semi and anti joins
    
    10. Subqueries
    
    11. CTEs and recursive CTEs
    
    12. UNION, INTERSECT, EXCEPT
    
    13. Window functions: ranking
    
    14. Window functions: LAG, LEAD and running totals
    
    15. Classic interview patterns
    
    16. Dates and time series
    
    17. INSERT, UPDATE, DELETE, MERGE
    
    18. CREATE TABLE, types, constraints
    
    19. Data modelling
    
    20. Transactions and isolation
    
    21. Views and materialized views
    
    22. Duplicates and incremental loads
    
    23. Data quality checks
    
    24. JSON and arrays
    
    25. Indexes and EXPLAIN
    
    26. Making slow queries fast
    
    27. GROUPING SETS, ROLLUP, CUBE, LATERAL
    
    28. chapter 28
    
    29. Safe SQL
    
    30. Practice set A
    
    31. Practice set B
    
    32. Mock tests
    
    Glossary

23. Data quality checks¶

Being written

This chapter is being written and will be here soon (November 2026).

22. Duplicates and incremental loads

24. JSON and arrays

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