Update DBMS/SQL/Week7/writeup.md

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-## Week 7 - DBMS Lab - PL SQL & Triggers
+## Week 7 - DBMS Lab - PL SQL & Triggers
+
+### DB
+
+```sql
+SQL> select table_name from user_tables;
+
+TABLE_NAME
+--------------------------------------------------------------------------------
+ACCIDENT
+CAR
+OWNS
+PARTICIPATED
+PERSON
+
+SQL> select * from accident;
+
+REPORT_NUMBER ACCD_DATE LOCATION
+------------- --------- --------------------------------------------------
+            1 01-JAN-24 Delhi India
+            3 29-FEB-24  India
+            5 31-MAR-00  Gujrat India
+           12 17-JUL-00  karnataka India
+
+SQL> select * from car;
+
+REGNO                MODEL                                YEAR
+-------------------- ------------------------------ ----------
+ABCD0001             Celtos                                  3
+EFGH2001             Ferrari                                32
+DSDS0001             Urus                                    5
+ABCD4001             Honda City                              1
+HFSP5601             mini cooper                             7
+
+SQL> select * from owns;
+
+DRIVER_ID#                     REGNO
+------------------------------ --------------------
+1234                           ABCD0001
+1235                           EFGH2001
+1236                           DSDS0001
+1237                           ABCD4001
+1238                           HFSP5601
+
+SQL> select * from participated;
+
+DRIVER_ID#                     REGNO                REPORT_NUMBER DAMAGE_AMOUNT
+------------------------------ -------------------- ------------- -------------
+1234                           ABCD0001                         1         10000
+1236                           DSDS0001                         3           150
+1238                           HFSP5601                         5          1500
+1238                           HFSP5601                        12         25000
+
+SQL> select * from person;
+
+DRIV NAME       ADDRESS
+---- ---------- ------------------------------
+1234 Rohan      Delhi India
+1237 Saarthak   Manipal India
+1236 Ramesh     Maharashtra India
+1235 Rohit      Banglalore India
+1238 Amogh      Muzaffarnagar
+```
+
+### Q1. Generate a trigger displaying driver information, on participating in an accident.
+
+Trigger:
+```sql
+CREATE OR REPLACE TRIGGER trg_display_driver_info
+AFTER INSERT ON participated
+FOR EACH ROW
+DECLARE
+    v_driver_name VARCHAR2(100);
+    v_driver_address VARCHAR2(255);
+BEGIN
+    -- Fetch driver information based on DRIVER_ID#
+    SELECT NAME, ADDRESS
+    INTO v_driver_name, v_driver_address
+    FROM person
+    WHERE DRIVER_ID# = :NEW.DRIVER_ID#;
+
+    -- Display the driver information
+    DBMS_OUTPUT.PUT_LINE('Driver ID: ' || :NEW.DRIVER_ID#);
+    DBMS_OUTPUT.PUT_LINE('Driver Name: ' || v_driver_name);
+    DBMS_OUTPUT.PUT_LINE('Driver Address: ' || v_driver_address);
+    DBMS_OUTPUT.PUT_LINE('Car Registration Number: ' || :NEW.REGNO);
+    DBMS_OUTPUT.PUT_LINE('Report Number: ' || :NEW.REPORT_NUMBER);
+    DBMS_OUTPUT.PUT_LINE('Damage Amount: ' || :NEW.DAMAGE_AMOUNT);
+END;
+/
+```
+
+Demo:
+```sql
+SQL> INSERT INTO participated (DRIVER_ID#, REGNO, REPORT_NUMBER, DAMAGE_AMOUNT)
+  2  VALUES (1235, 'EFGH2001', 3, 5000);
+Driver ID: 1235
+Driver Name: Rohit
+Driver Address: Banglalore India
+Car Registration Number: EFGH2001
+Report Number: 3
+Damage Amount: 5000
+Driver_id: 1235 Name: Rohit Address: Banglalore India
+
+1 row created.
+```
+
+### Q2. 
+
+
+
+### Q3. List cars involved in accidents with cumulative damage exceeding a specific amount.
+
+Checking for damage amount > 10000, we have
+```SQL
+SQL> SELECT
+          p.driver_id#,
+          o.regno,
+          SUM(pa.damage_amount) AS total_damage
+      FROM
+          PARTICIPATED pa
+      JOIN
+          OWNS o ON pa.driver_id# = o.driver_id#
+      JOIN
+          PERSON p ON o.driver_id# = p.driver_id#
+      GROUP BY
+          p.driver_id#, o.regno
+      HAVING
+          SUM(pa.damage_amount) > 10000;
+
+DRIVER_ID#                     REGNO                TOTAL_DAMAGE
+------------------------------ -------------------- ------------
+1238                           HFSP5601                    26500
+```
+
+### Q4. Identify cars that have been involved in more than one accident and calculate the total damage for each car.
+
+```SQL
+SQL> SELECT 
+    o.regno, 
+    COUNT(DISTINCT pa.report_number) AS accident_count, 
+    SUM(pa.damage_amount) AS total_damage
+FROM 
+    PARTICIPATED pa
+JOIN 
+    OWNS o ON pa.driver_id# = o.driver_id#
+GROUP BY 
+    o.regno
+HAVING 
+    COUNT(DISTINCT pa.report_number) > 1;
+
+REGNO                ACCIDENT_COUNT TOTAL_DAMAGE
+-------------------- -------------- ------------
+HFSP5601                          2        26500
+```
+
+### Q5. Calculate the average damage amount for accidents at each location.
+```sql
+SQL> SELECT
+          a.location,
+          AVG(pa.damage_amount) AS average_damage
+      FROM
+          ACCIDENT a
+      JOIN
+          PARTICIPATED pa ON a.report_number = pa.report_number
+      GROUP BY
+          a.location;
+
+LOCATION                                           AVERAGE_DAMAGE
+-------------------------------------------------- --------------
+ karnataka India                                            25000
+Delhi India                                                 10000
+ India                                                       2575
+ Gujrat India                                                1500
+ ```