Features
SQL CASE WHEN ELSE lets you return different values in the same column by evaluating conditions in order and outputting the first matching result, with ELSE as a fallback.
SQL CASE WHEN ELSE lets you return different values in the same column based on conditional logic, similar to IF-THEN-ELSE in programming.
SQL CASE WHEN ELSE is a conditional expression that evaluates predicates sequentially and returns the first matched result, enabling row-level logic without joins or subqueries.
Use CASE WHEN ELSE to categorize data, build conditional aggregations, replace NULLs, and craft dynamic labels inside SELECT, UPDATE, ORDER BY, or WHERE clauses.
CASE starts, each WHEN holds a boolean test, THEN defines the return value, ELSE provides a fallback, and END closes the block; evaluation stops at the first true WHEN.
CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ELSE default END is the searched form; the scalar form compares one expression to many literals.
Scalar CASE evaluates a single expression against constants, while searched CASE evaluates independent conditions, offering maximum flexibility for complex filters.
Turn scores into letter grades directly in the SELECT list.SELECT score,
CASE
WHEN score >= 90 THEN 'A'
WHEN score >= 80 THEN 'B'
ELSE 'C or below'
END AS grade
FROM exams;
Compute multiple metrics in one scan with COUNT and CASE.SELECT
COUNT(*) AS orders_total,
COUNT(CASE WHEN status = 'shipped' THEN 1 END) AS orders_shipped
FROM orders;
Switch filters based on a parameterized flag.WHERE
CASE :filterBy
WHEN 'country' THEN country
WHEN 'state' THEN state
END = :value
Avoid non-deterministic functions in CASE conditions to preserve index usage and plan caching.
Always add ELSE to avoid implicit NULLs and make downstream handling explicit.
Align WHEN clauses, indent clearly, and give descriptive aliases, ensuring future maintainers understand the logic.
1 – Order matters: place specific predicates before general ones or they will never match.2 – Datatype mismatch: ensure all THEN and ELSE results share a compatible datatype to prevent implicit casts.3 – Overusing CASE: move overly complex logic to staging tables or CTEs for clarity and performance.
Galaxy’s AI copilot autocompletes CASE syntax, warns about datatype mismatches, and lets teams endorse the final query so everyone reuses the same conditional logic safely.
CASE evaluates row-by-row; index referenced columns and avoid wrapping indexed fields in functions to keep scans efficient.
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Conditional logic is essential for analytics and data engineering. CASE WHEN ELSE allows transformations, bucketing, and dynamic labeling to happen in-database, reducing data movement and simplifying pipelines. Analysts can build single-pass reports, engineers avoid brittle application logic, and BI tools gain flexibility without extra tables.
No. If you omit ELSE, unmatched rows return NULL. Adding ELSE improves clarity and avoids unexpected NULLs.
Yes. You can place a CASE inside another CASE’s THEN or ELSE, but keep nesting shallow for readability.
Minor CPU overhead is added, but the expression is computed during the scan. Indexed predicates and selective filtering keep execution fast.
Galaxy’s AI copilot autocompletes CASE syntax, suggests predicate ordering, and flags datatype mismatches, speeding up query authoring.
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