Added queries and softcopy for assignment A6.

Practical/Assignment-A6/Queries-A6.md

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+## Creating tables
+
+`O_RollCall` table:
+```sql
+CREATE TABLE O_RollCall(
+name VARCHAR(255),
+roll NUMBER(14),
+class VARCHAR(255)
+);
+
+```
+
+`N_RollCall` table:
+```sql
+CREATE TABLE N_RollCall(
+name VARCHAR(255),
+roll NUMBER(14),
+class VARCHAR(255)
+);
+
+```
+
+## Inserting data
+
+`O_RollCall` table:
+```sql
+INSERT INTO O_RollCall VALUES ('Stewie', 1, 'Comp 1');
+INSERT INTO O_RollCall VALUES ('Edie', 2, 'Comp 2');
+INSERT INTO O_RollCall VALUES ('Stomp', 3, 'Comp 3');
+INSERT INTO O_RollCall VALUES ('Lara', 4, 'Comp 1');
+INSERT INTO O_RollCall VALUES ('Foxy', 5, 'Comp 2');
+
+```
+
+`N_RollCall` table:
+```sql
+INSERT INTO N_RollCall VALUES ('Stewie', 1, 'Comp 1');
+INSERT INTO N_RollCall VALUES ('Edie', 2, 'Comp 2');
+INSERT INTO N_RollCall VALUES ('Stomp', 3, 'Comp 3');
+INSERT INTO N_RollCall VALUES ('Lara', 4, 'Comp 1');
+INSERT INTO N_RollCall VALUES ('Foxy', 5, 'Comp 2');
+INSERT INTO N_RollCall VALUES ('Gundeti', 6, 'Comp 3');
+INSERT INTO N_RollCall VALUES ('Kalas', 7, 'Comp 2');
+
+```
+
+## Procedure
+
+### Explicit cursor
+```sql
+DECLARE
+  p_name VARCHAR(255);
+  p_rollno NUMBER(15);
+  p_class VARCHAR(255);
+  CURSOR cc1 IS SELECT * FROM N_RollCall WHERE roll NOT IN (SELECT roll FROM O_RollCall);
+BEGIN
+  OPEN cc1;
+    LOOP
+      FETCH cc1 INTO p_name, p_rollno, p_class;
+      INSERT INTO O_RollCall VALUES (p_name, p_rollno, p_class);
+      EXIT WHEN cc1%notfound;
+      DBMS_OUTPUT.PUT_LINE(p_name || ' ' || p_rollno || ' ' || p_class);
+      END LOOP;
+  CLOSE cc1;
+END;
+/
+
+```
+
+### Parameterized cursor
+```sql
+DECLARE
+  p_name VARCHAR(255);
+  p_rollno NUMBER(15);
+  p_class VARCHAR(255);
+  CURSOR pp1(roll1 NUMBER) IS SELECT * FROM N_RollCall WHERE roll > roll1;
+
+BEGIN
+  OPEN pp1(3);
+    LOOP
+      FETCH pp1 INTO p_name, p_rollno, p_class;
+      EXIT WHEN pp1%notfound;
+      DBMS_OUTPUT.PUT_LINE(p_name || ' ' || p_rollno || ' ' || p_class);
+    END LOOP;
+  CLOSE pp1;
+
+END;
+/
+
+```
+
+### Implicit Cursor
+```sql
+DECLARE
+  total_rows NUMBER(2);
+
+BEGIN
+  UPDATE N_RollCall SET roll = roll + 1;
+  IF sql%notfound THEN
+    dbms_output.put_line('no roll was updated');
+  ELSIF sql%found THEN
+    total_rows := sql%rowcount;
+    DBMS_OUTPUT.PUT_LINE( total_rows || ' roll calls were affected ');
+  END IF;
+END;
+/
+
+```