substring error

Category: Data ExceptionVersions: All Postgres versions

What this means

SQLSTATE 22011 is raised when arguments to the SUBSTRING function are invalid — for example, a negative or zero length argument in contexts where the standard requires validation.

Why it happens

1Invalid from/for arguments to SUBSTRING that violate the SQL standard length requirements

How to reproduce

SUBSTRING with an invalid length argument.

trigger — this will ERROR

SELECT SUBSTRING('hello' FROM 2 FOR -1);

ERROR: negative substring length not allowed

Fix 1: Ensure SUBSTRING arguments are non-negative

When using SUBSTRING with computed arguments.

fix

SELECT SUBSTRING('hello' FROM 2 FOR GREATEST(len_val, 0));

Why this works

GREATEST clamps the length to 0 or above. A FOR 0 returns an empty string, which is usually safer than an error.

Sources

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

🔧 Source ref: Class 22 — Data Exception

Confidence assessment

✅ HIGH confidence

Standard SQLSTATE for SUBSTRING argument validation. Stable across versions.