division_by_zero division by zero — 22012

Symptoms

An arithmetic expression divided by zero — with /, the modulo operator %, or a function such as div(). SQL has no defined result for division by zero, so PostgreSQL raises an error instead of returning a value.

• The statement aborts with SQLSTATE 22012.
• Typically one or more rows have a zero divisor.
• Often surfaces when computing ratios or percentages over real data.

What the server log shows

ERROR:  division by zero
STATEMENT:  SELECT revenue / quantity FROM sales;

Why PostgreSQL raises this — what the manual says

As Section 9.3 Mathematical Functions and Operators explains:

Division by zero is mathematically undefined, so the division (/) and modulo (%) operators raise a division-by-zero error rather than returning a value when the divisor is zero.

When the divisor of / or % evaluates to zero (integer, numeric, or floating types alike) the operator raises 22012 and the statement aborts. The usual trigger is a per-row divisor column that contains a zero for some rows.

Common causes

• A divisor column or expression that is zero for some rows.
• Computing a ratio/percentage before filtering out zero denominators.
• An aggregate denominator that turns out to be zero.

How to fix it

1. Guard the divisor with NULLIF: revenue / NULLIF(quantity, 0) (yields NULL instead of erroring).
2. Filter zero rows: WHERE quantity <> 0.
3. Use a CASE expression to choose a fallback when the divisor is zero.
4. Validate inputs so denominators are never zero.

Diagnostic query

-- Find the rows that would divide by zero
SELECT * FROM sales WHERE quantity = 0;

These rows are the ones triggering the error.

Related & next steps

• SQLSTATE 22012 — Division By Zero (full reference)
• Message: numeric field overflow
• Message: invalid input syntax for type numeric

Reference: PostgreSQL 18 Section 9.3 “Mathematical Functions and Operators”.