postgresql/no-distinct-on-without-order-by

Why this matters

Without `ORDER BY`, PostgreSQL keeps an arbitrary row from each group of `DISTINCT ON` — the result depends on scan order and changes silently across plan or stats updates. Pair `DISTINCT ON` with an `ORDER BY` whose leading columns match.

Examples

SELECT DISTINCT ON (customer_id) customer_id, amount FROM orders;

SELECT DISTINCT ON (customer_id) customer_id, amount
FROM orders
ORDER BY customer_id, created_at DESC;

SELECT DISTINCT customer_id FROM orders;

Configure it

// eslint.config.js
import postgresql from "eslint-plugin-postgresql";

export default [
  {
    files: ["**/*.sql"],
    languageOptions: {
      parser: postgresql.configs.recommended.languageOptions.parser,
    },
    plugins: { postgresql },
    rules: {
      "postgresql/no-distinct-on-without-order-by": "error",
    },
  },
];

Options

This rule has no options.