1. Create a table called EMP with the following structure. Name Type EMPNO NUMBER (6) ENAME VARCHAR2 (20) JOB VARCHAR2 (10) DEPTNO NUMBER (3) SAL NUMBER (7,2) Allow NULL for all columns except ename and job. 2. Add constraints to check, while entering the empno value (i.e) empno > 100. 3. Define the field DEPTNO as unique. 4. Create a primary key constraint for the table(EMPNO). 5. Write queries to implement and practice constraints.

Here are the SQL commands to perform the tasks you've described:

1. Create the EMP table:

CREATE TABLE EMP (
    EMPNO NUMBER(6),
    ENAME VARCHAR2(20) NOT NULL,
    JOB VARCHAR2(10) NOT NULL,
    DEPTNO NUMBER(3),
    SAL NUMBER(7,2)
);

2. Add a constraint to check the EMPNO value:

ALTER TABLE EMP
ADD CONSTRAINT EMPNO_CHECK CHECK (EMPNO > 100);

3. Define the DEPTNO field as unique:

ALTER TABLE EMP
ADD CONSTRAINT DEPTNO_UNIQUE UNIQUE (DEPTNO);

4. Create a primary key constraint for the EMPNO field:

ALTER TABLE EMP
ADD CONSTRAINT EMPNO_PK PRIMARY KEY (EMPNO);

5. To practice constraints, you can try inserting some data into the table. For example:

-- This should succeed
INSERT INTO EMP (EMPNO, ENAME, JOB, DEPTNO, SAL) VALUES (101, 'John', 'Engineer', 1, 5000.00);

-- This should fail because EMPNO is not > 100
INSERT INTO EMP (EMPNO, ENAME, JOB, DEPTNO, SAL) VALUES (99, 'Jane', 'Analyst', 2, 6000.00);

-- This should fail because ENAME is NULL
INSERT INTO EMP (EMPNO, JOB, DEPTNO, SAL) VALUES (102, 'Manager', 3, 7000.00);

-- This should fail because DEPTNO is not unique
INSERT INTO EMP (EMPNO, ENAME, JOB, DEPTNO, SAL) VALUES (103, 'Mike', 'Engineer', 1, 8000.00);

-- This should fail because EMPNO is not unique (primary key violation)
INSERT INTO EMP (EMPNO, ENAME, JOB, DEPTNO, SAL) VALUES (101, 'Anna', 'Analyst', 4, 9000.00);

Remember to commit your changes after each successful insert:

COMMIT;