Comprehension: Consider the following table structures related to a university for given questions.
EMPLOYEE
|
NAME |
VARCHAR (30) |
NOT NULL, |
|
EID |
VARCHAR (10) |
NOT NULL, |
|
DEPTNO |
INT (5) |
NOT NULL, |
|
HODEID |
VARCHAR (10), |
|
|
SALARY |
INT (10), |
|
PRIMARY KEY (EID),
FOREIGN KEY (HODEID) REFRENCES EMPLOYEE (EID),
FOREIGN KEY (DEPTNO) REFRENCES DEPARTMENT (DID);
DEPARTMENT
|
DID |
INT (5) |
NOT NULL, |
|
DNAME |
VARCHAR (30) |
NOT NULL, |
|
HODID |
VARCHAR (10) |
NOT NULL, |
|
HODNAME |
VARCHAR (30), |
|
PRIMARY KEY (DID),
UNIQUE (DNAME),
FOREIGN KEY (HODID) REFERENCES EMPLOYEE (EID),
PROJECT WORE:
|
EMPID |
VARCHAR (10) |
NOT NULL, |
|
PROJNO |
INT (5) |
NOT NULL, |
|
PROJECTLOC |
VARCHAR (30) |
NOT NULL, |
PRIMARY KEY (EMPID, PROJNQ),
FOREIGN KEY (EMPID) REFERENCES EMPLOYEE (EID),
On the basis of above given table structures, retrieve the distinct employee ID (EMPID) of all employees of university who are working on project No.20, 30 and 40.
SELECT EMPID
FROM PROJECTWORK
WHERE PROJNO=(20, 30, 40);
SELECT EMPID
FROM PROJECTWOREK
WHERE PROJNO IN (20, 30, 40);
SELECT DISTINCT EMPID
FROM PROJECTWORK
WHERE PROJNO IN (20, 30, 40);
SELECT DISTINCT EMPID
FROM PROJECTWORK
WHERE PROJNO=20, 30, 40;