The case_not_found error (SQLSTATE 20000) occurs when a CASE expression or searched CASE statement finds no matching WHEN clause and lacks an ELSE branch.
case_not_found in PostgreSQL signals that a CASE expression returned no result because none of the WHEN clauses matched and no ELSE clause was supplied. Add a safe ELSE branch or ensure every possible value is covered to resolve the error.
case_not_found
The case_not_found error (SQLSTATE 20000) appears when a CASE expression executes but fails to return a value. PostgreSQL raises the exception because no WHEN clause matched and the expression lacks an ELSE branch.
The error usually surfaces in SELECT lists, computed columns, PL/pgSQL assignments, or constraint definitions that rely on CASE.
Fixing it is critical because the query aborts, transactions roll back, and applications may crash or display incorrect data.
PostgreSQL expects each CASE expression to resolve to a single value. Omitting an ELSE branch leaves a gap when none of the WHEN conditions evaluate to TRUE.
At runtime, the engine throws case_not_found rather than return NULL.
The error can also occur when expression results are NULL and none of the WHEN tests account for NULL comparisons, because NULL = value evaluates to FALSE.
Add an ELSE clause that returns a default value such as NULL, 0, or a sentinel string. Alternatively, expand the WHEN list so every valid input is covered.
Refactor logic into COALESCE or NULLIF functions if appropriate.
In PL/pgSQL, use EXCEPTION blocks to catch and handle SQLSTATE '20000' when you intentionally allow gaps. Catching the error lets you substitute a safe value without aborting the function.
Column categorization often misses a boundary value, for example WHEN score >= 90 THEN 'A' ... ELSE 'F'. Verify the predicate ranges overlap and cover NULLs.
Data type mismatches between compared values can silently fail to match.
Ensure you compare with compatible types or cast properly.
Always include an ELSE branch returning a harmless default. Review CASE blocks during code review for total branch coverage.
Add unit tests or CHECK constraints that force all possible inputs through the CASE to detect gaps early. Enable strict linting rules in Galaxy or CI pipelines.
no_data_found (SQLSTATE P0002) fires when SELECT INTO finds no rows.
too_many_rows (P0003) occurs when SELECT INTO finds more than one row. Both are handled similarly with EXCEPTION blocks.
division_by_zero (22012) surfaces when dividing by zero. Prevent by wrapping divisor in NULLIF or CASE with an ELSE 0 branch.
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No. It is a standards-compliant runtime safeguard that alerts you to an incomplete CASE expression.
Yes. Add ELSE NULL to the CASE block so PostgreSQL returns NULL rather than raising the error.
Yes. Unless caught in PL/pgSQL, the exception aborts the current transaction block.
Galaxy's AI copilot and static analysis highlight CASE blocks missing ELSE clauses as you type, preventing runtime failures.
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