add nth_value and update ordering

docs/en/sql-reference/window-functions/index.md

@@ -78,11 +78,11 @@ These functions can be used only as a window function.
 - [`row_number()`](./row_number.md) - Number the current row within its partition starting from 1.
 - `first_value(x)` - Return the first non-NULL value evaluated within its ordered frame.
 - `last_value(x)` -	Return the last non-NULL value evaluated within its ordered frame.
-- `nth_value(x, offset)` - Return the first non-NULL value evaluated against the nth row (offset) in its ordered frame.
+- [`nth_value(x, offset)`](./nth_value.md) - Return the first non-NULL value evaluated against the nth row (offset) in its ordered frame.
 - [`rank()`](./rank.md) - Rank the current row within its partition with gaps.
 - [`dense_rank()`](./dense_rank.md) - Rank the current row within its partition without gaps.
-- `lagInFrame(x)` - Return a value evaluated at the row that is at a specified physical offset row before the current row within the ordered frame.
-- `leadInFrame(x)` - Return a value evaluated at the row that is offset rows after the current row within the ordered frame.
+- [`lagInFrame(x)`](./lagInFrame.md) - Return a value evaluated at the row that is at a specified physical offset row before the current row within the ordered frame.
+- [`leadInFrame(x)`](./leadInFrame.md) - Return a value evaluated at the row that is offset rows after the current row within the ordered frame.
 
 ## Examples
 

docs/en/sql-reference/window-functions/lagInFrame.md

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 slug: /en/sql-reference/window-functions/lagInFrame
 sidebar_label: lagInFrame
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 # lagInFrame

docs/en/sql-reference/window-functions/leadInFrame.md

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 slug: /en/sql-reference/window-functions/leadInFrame
 sidebar_label: leadInFrame
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 # leadInFrame

docs/en/sql-reference/window-functions/nth_value.md

@@ -0,0 +1,77 @@
+---
+slug: /en/sql-reference/window-functions/leadInFrame
+sidebar_label: leadInFrame
+sidebar_position: 5
+---
+
+# nth_value
+
+Return the first non-NULL value evaluated against the nth row (offset) in its ordered frame.
+
+The [dense_rank](./dense_rank.md) function provides the same behaviour but without gaps in ranking.
+
+**Syntax**
+
+```sql
+nth_value (x, offset)
+  OVER ([[PARTITION BY grouping_column] [ORDER BY sorting_column] 
+        [ROWS or RANGE expression_to_bound_rows_withing_the_group]] | [window_name])
+FROM table_name
+WINDOW window_name as ([[PARTITION BY grouping_column] [ORDER BY sorting_column])
+```
+
+For more detail on window function syntax see: [Window Functions - Syntax](./index.md/#syntax).
+
+**Parameters**
+
+- `x` — Column name.
+- `offset` — nth row to evaluate current row against.
+
+**Returned value**
+
+- The first non-NULL value evaluated against the nth row (offset) in its ordered frame.
+
+**Example**
+
+In this example the `nth-value` function is used to find the third-highest salary from a fictional dataset of salaries of Premier League football players.
+
+Query:
+
+```sql
+DROP TABLE IF EXISTS salaries;
+CREATE TABLE salaries
+(
+    `team` String,
+    `player` String,
+    `salary` UInt32,
+    `position` String
+)
+Engine = Memory;
+
+INSERT INTO salaries FORMAT Values
+    ('Port Elizabeth Barbarians', 'Gary Chen', 195000, 'F'),
+    ('New Coreystad Archdukes', 'Charles Juarez', 190000, 'F'),
+    ('Port Elizabeth Barbarians', 'Michael Stanley', 10000, 'D'),
+    ('New Coreystad Archdukes', 'Scott Harrison', 180000, 'D'),
+    ('Port Elizabeth Barbarians', 'Robert George', 195000, 'M'),
+    ('South Hampton Seagulls', 'Douglas Benson', 150000, 'M'),
+    ('South Hampton Seagulls', 'James Henderson', 140000, 'M');
+```
+
+```sql
+SELECT salary, nth_value(salary,3) OVER(ORDER BY salary DESC) FROM salaries GROUP BY salary;
+```
+
+Result:
+
+```response
+   ┌─player──────────┬─salary─┬─rank─┐
+1. │ Gary Chen       │ 195000 │    1 │
+2. │ Robert George   │ 195000 │    1 │
+3. │ Charles Juarez  │ 190000 │    3 │
+4. │ Douglas Benson  │ 150000 │    4 │
+5. │ Michael Stanley │ 150000 │    4 │
+6. │ Scott Harrison  │ 150000 │    4 │
+7. │ James Henderson │ 140000 │    7 │
+   └─────────────────┴────────┴──────┘
+```

docs/en/sql-reference/window-functions/rank.md

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 slug: /en/sql-reference/window-functions/rank
 sidebar_label: rank
-sidebar_position: 3
+sidebar_position: 6
 ---
 
 # rank

docs/en/sql-reference/window-functions/row_number.md

@@ -1,7 +1,7 @@
 ---
 slug: /en/sql-reference/window-functions/row_number
 sidebar_label: row_number
-sidebar_position: 4
+sidebar_position: 7
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 # row_number