Create ratio_to_report.md

Author: structured-query-language

ratio_to_report.md

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+# Calculating percentages using RATIO_TO_REPORT
+
+RATIO_TO_REPORT Window function can be used to calculate percentage of the entire dataset or partitioned data.
+
+## An illustrative example
+
+Let’s look at the dataset we will be using for this tutorial:
+
+```sql
+select
+    player_id,
+    team,
+    position,
+    goals,
+from soccer_players
+```
+
+![Copy of Copy of favicon](https://github.com/user-attachments/assets/b953283b-3504-42ab-80d8-202c03d14cd7)
+
+Our data is about a soccer game where each row represents a player id, with columns for id, their team, and how many goals they have scored.
+
+If we wanted to work out what percentage of all goal each player has scored, we can use ratio_to_report() window function as following:
+
+```sql
+select
+    player_id,
+    team,
+    position,
+    goals,
+    ratio_to_report(goals) over () as overall_goals_percentage
+from soccer_players
+order by team, position;
+```
+
+![Copy of Copy of Copy of favicon](https://github.com/user-attachments/assets/c0219bc2-6030-4fcb-a34e-c8523c48d07c)
+
+
+The over() in the query above tells the database to expand the ‘window’ in which the ratio_to_report() operates to the whole dataset.
+
+The ratio_to_report() window function takes an expression (usually a column) as input and calculates the ratio of that expression to the window that is defined (in this case, the whole dataset).
+Using ratio_to_report() to Calculate Partitioned Percentages
+
+Let’s say we were not only interested in each players overall contribution to goals, but also their contribution to goals for their specific team. We can then add a partition by to the window:
+
+```sql
+select
+    player_id,
+    team,
+    position,
+    goals,
+    ratio_to_report(goals) over (team) as overall_goals_percentage
+from soccer_players
+order by team, position;
+```
+
+![Copy of favicon](https://github.com/user-attachments/assets/29fa93bc-61d8-436a-8d92-fc539fdbd243)