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PostgreSQL error code

PostgreSQL error 42804

42804 is the SQLSTATE PostgreSQL reports for datatype mismatch, in class 42, Syntax Error or Access Rule Violation.

SQLSTATE42804
Condition namedatatype_mismatch
Class42 — Syntax Error or Access Rule Violation

Reproduce it, then fix it

WHERE needs a boolean. MySQL and SQLite treat a non-zero number as true, but PostgreSQL makes you write the comparison. Run the broken query to see the error, then switch to the fixed one. Edit either freely; every run is rolled back.

SELECT name FROM products WHERE stock_quantity;
SELECT name FROM products WHERE stock_quantity > 0;

Source: PostgreSQL documentation, Appendix A