How to Convert DELETE with JOIN from SQL Server to PostgreSQL

You ran DELETE t1 FROM Table1 t1 JOIN Table2... on PostgreSQL and got a syntax error. That is expected: T-SQL allows aliases and JOIN directly in DELETE; PostgreSQL does not.

The practical rule: in Postgres use DELETE ... USING other_tables or rewrite with a subquery / NOT EXISTS when the JOIN is LEFT and you filter orphan rows.

Before (SQL Server)

DELETE t
FROM Items t
INNER JOIN Orders p ON t.OrderId = p.Id
WHERE p.Status = 'CANCELLED';

After (PostgreSQL — USING)

DELETE FROM items t
USING orders p
WHERE t.order_id = p.id
  AND p.status = 'CANCELLED';

DELETE with LEFT JOIN

When the filter is IS NULL on the right side (anti-join), USING does not reproduce the same semantics. The safe pattern is NOT EXISTS.

DELETE t FROM Items t
LEFT JOIN Stock e ON t.Id = e.ItemId
WHERE e.ItemId IS NULL;

DELETE FROM items t
WHERE NOT EXISTS (
  SELECT 1 FROM stock e WHERE e.item_id = t.id
);