Update DBMS/SQL/Week7/writeup.md

DBMS/SQL/Week7/writeup.md

@@ -41,8 +41,69 @@ Driver_id: 1235 Name: Rohit Address: Banglalore India
 1 row created.
 ```
 
-### Q2. 
+### Q2. Create a trigger that updates a `total_damage` column in the `accident` table whenever a new entry is added to or removed from the participated field.`
 
+```SQL
+SQL> CREATE OR REPLACE TRIGGER update_total_damage
+  2  AFTER
+  3    INSERT OR DELETE ON PARTICIPATED
+  4  BEGIN
+  5    UPDATE ACCIDENT
+  6    SET
+  7      total_damage = (
+  8        SELECT
+  9          SUM(damage_amount)
+ 10        FROM PARTICIPATED p
+ 11        WHERE
+ 12          p.report_number = ACCIDENT.report_number
+ 13      );
+ 14  END;
+ 15  /
+
+Trigger created.
+```
+```sql
+SQL> ALTER TABLE ACCIDENT ADD total_damage NUMBER;
+```
+```sql
+SQL> INSERT INTO
+        PARTICIPATED (driver_id#, regno, report_number, damage_amount)
+      VALUES
+        ('1235', 'EFGH2001', 1, 5000);
+Driver_id: 1235 Name: Rohit Address: Banglalore India
+
+1 row created.
+
+SQL> SELECT
+        report_number,
+        total_damage
+      FROM ACCIDENT
+      WHERE
+        report_number = 1;
+
+REPORT_NUMBER TOTAL_DAMAGE
+------------- ------------
+            1        15000
+
+SQL> DELETE FROM PARTICIPATED
+      WHERE
+        driver_id# = '1235'
+        AND regno = 'EFGH2001'
+        AND report_number = 1;
+
+1 row deleted.
+
+SQL> SELECT
+        report_number,
+        total_damage
+      FROM ACCIDENT
+      WHERE
+        report_number = 1;
+
+REPORT_NUMBER TOTAL_DAMAGE
+------------- ------------
+            1        10000
+```
 
 
 ### Q3. List cars involved in accidents with cumulative damage exceeding a specific amount.