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Introduction
ROWS
6. Window frame definition
RANGE
Default window frame
Summary

## Instruction

Okay. Let's jump into the brackets of OVER(...) and discuss the details. We'll start with ROWS, because they are a bit easier to explain than RANGE. The general syntax is as follows:

ROWS BETWEEN lower_bound AND upper_bound

You know BETWEEN already – it's used to define a range. So far, you've used it to define a range of values – this time, we're going to use it to define a range of rows instead. What are the two bounds? The bounds can be any of the five options:

• UNBOUNDED PRECEDING – the first possible row.
• PRECEDING – the n-th row before the current row (instead of n, write the number of your choice).
• CURRENT ROW – simply current row.
• FOLLOWING – the n-th row after the current row.
• UNBOUNDED FOLLOWING – the last possible row.

The lower bound must come BEFORE the upper bound. In other words, a construction like: ...ROWS BETWEEN CURRENT ROW AND UNBOUNDED PRECEDING doesn't make sense and you'll get an error if you run it.

## Exercise

Take a look at the example on the right. The query computes:

• the total price of all orders placed so far (this kind of sum is called a running total),
• the total price of the current order, 3 preceding orders and 3 following orders.