Database.Middle.If i don’t use ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW, so i take all rows ?

Excellent question — and the answer depends on which window function you’re using, and whether you’re using ORDER BY in the OVER() clause.

Let’s clarify it fully:

---

✅ If You Use ORDER BY Without ROWS BETWEEN

When you write something like:

SUM(sale_amount) OVER (
  PARTITION BY employee_id
  ORDER BY sale_date
)

You are implicitly using:

ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW

✅ So YES — it’s the same as using it explicitly.

🧪 What Happens Under the Hood

The default window frame depends on what you specify:

Clause Used	Interpreted As
ORDER BY (without ROWS BETWEEN)	ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
No ORDER BY	RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING (entire partition)

---

🧾 Example 1: With ORDER BY

SUM(sale_amount) OVER (
  PARTITION BY employee_id
  ORDER BY sale_date
)

→ Behaves like a running total

---

🧾 Example 2: Without ORDER BY

SUM(sale_amount) OVER (
  PARTITION BY employee_id
)

→ Behaves like SUM() per group (same result for every row in the partition), because it considers all rows in the partition.

🧠 Summary

Situation	Window Frame Used
PARTITION BY + ORDER BY	ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
PARTITION BY only (no ORDER BY)	RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING (entire group)
Explicit ROWS BETWEEN clause	As specified