42P08ERRORTier 2 — Caution✅ HIGH confidence

ambiguous parameter

Category: Syntax Error or Access Rule ViolationVersions: All Postgres versions

What this means

SQLSTATE 42P08 is raised when a query parameter ($n) is ambiguous because it appears in a context where Postgres cannot determine its type and multiple type interpretations are possible.

Why it happens

1A query parameter used in an expression that could be resolved to multiple different types, making Postgres unable to pick one

How to reproduce

Ambiguous parameter type in a prepared statement.

trigger — this will ERROR

ERROR: could not determine data type of parameter $1

Fix 1: Specify the parameter type explicitly in PREPARE

When Postgres cannot infer the type of a parameter.

fix

PREPARE stmt (TEXT) AS SELECT * FROM orders WHERE status = $1;

Why this works

Providing the parameter types in PREPARE eliminates type ambiguity.

Sources

📚 Official docs: https://www.postgresql.org/docs/current/errcodes-appendix.html

🔧 Source ref: Class 42 — Syntax Error or Access Rule Violation (Postgres-specific)

Confidence assessment

✅ HIGH confidence

Postgres-specific. Stable across versions.