Added Messages Exchanged

Author: thecoddiwompler

Messages Exchanged/READme.md

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+# Messages Exchanged
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+
+---
+
+## 🛠️ Problem Statement
+
+
+  <b>Table Name : subscriber</b>
+</br>
+|  Column Name  |Type |
+| ------------- | ------------- |
+| sms_date  | date  |
+| sender  | varchar(20)  |
+| receiver  | varchar(20) |
+| sms_no  | int  |
+
+Each row contains information about the messages exchanged between two people on the given sms_date.
+
+
+Write a SQL query to fnd the total number of messages exchanged between each person each day in the "subscriber" table.
+</br>
+</br>
+Return the ouput in any order. <br><br>
+<b>The query result format is in the following example:  </b>
+</br>
+</br>
+
+ <details>
+<summary>
+Input
+</summary>
+<br>
+
+<b>Table Name : subscriber</b>
+
+| sms_date   | sender   | receiver | sms_no |
+|------------|----------|----------|--------|
+| 2020-04-01   | Avinash  | Vibhor   | 10     |
+| 2020-04-01   | Vibhor   | Avinash  | 20     |
+| 2020-04-01   | Avinash  | Pawan    | 30     |
+| 2020-04-01   | Pawan    | Avinash  | 20     |
+| 2020-04-01   | Vibhor   | Pawan    | 5      |
+| 2020-04-01   | Pawan    | Vibhor   | 8      |
+| 2020-04-01   | Vibhor   | Deepak   | 50     |
+
+
+</details>
+
+<details>
+<summary>
+Output
+</summary>
+<br>
+
+| sms_date   | p1       | p2      | total_sms |
+|------------|----------|---------|-----------|
+| 2020-04-01 | Deepak  | Avinash  | 0        |
+| 2020-04-01 | Pawan  | Avinash   | 50        |
+| 2020-04-01 | Pawan  | Deepak  | 0         |
+| 2020-04-01 | Vibhor    | Avinash  | 30        |
+| 2020-04-01 | Vibhor    | Deepak  | 50         |
+| 2020-04-01 | Vibhor   | Pawan  | 13       |
+
+
+</details>
+
+---

Messages Exchanged/schema.sql

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+CREATE TABLE subscriber (
+    sms_date date,
+    sender varchar(20),
+    receiver varchar(20),
+    sms_no int
+);
+
+-- insert some values
+
+INSERT INTO
+    subscriber (date, sender, receiver, amount)
+VALUES
+    ('2020-4-1', 'Avinash', 'Vibhor', 10),
+    ('2020-4-1', 'Vibhor', 'Avinash', 20),
+    ('2020-4-1', 'Avinash', 'Pawan', 30),
+    ('2020-4-1', 'Pawan', 'Avinash', 20),
+    ('2020-4-1', 'Vibhor', 'Pawan', 5),
+    ('2020-4-1', 'Pawan', 'Vibhor', 8),
+    ('2020-4-1', 'Vibhor', 'Deepak', 50);
+
+COMMIT;

Messages Exchanged/solution.sql

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+WITH recursive all_dates AS (
+    SELECT
+        MIN(sms_date) sms_date
+    FROM
+        subscriber
+    UNION
+    SELECT
+        sms_date + 1
+    FROM
+        all_dates
+    WHERE
+        sms_date + 1 <=(
+            SELECT
+                MAX(sms_date)
+            FROM
+                subscriber
+        )
+),
+person AS (
+    SELECT
+        DISTINCT sender person
+    FROM
+        subscriber
+    UNION
+    SELECT
+        DISTINCT receiver
+    FROM
+        subscriber
+),
+all_person AS (
+    SELECT
+        person,
+        ROW_NUMBER() over(
+            ORDER BY
+                person
+        ) rn
+    FROM
+        person
+),
+cte AS (
+    SELECT
+        c.sms_date,
+        a.person p1,
+        b.person p2
+    FROM
+        all_person a
+        INNER JOIN all_person b ON a.rn > b.rn
+        CROSS JOIN all_dates c
+)
+SELECT
+    a.sms_date,
+    a.p1,
+    a.p2,
+    COALESCE(sum(sms_no), 0) total_sms
+FROM
+    cte a
+    LEFT OUTER JOIN subscriber b ON a.sms_date = b.sms_date
+    AND (
+        (
+            a.p1 = b.sender
+            AND a.p2 = b.receiver
+        )
+        OR (
+            a.p2 = b.sender
+            AND a.p1 = b.receiver
+        )
+    )
+GROUP BY
+    a.sms_date,
+    a.p1,
+    a.p2;