Which of the following can be declared once in a table double varchar LONG mcq
Which of the following statements are TRUE about an SQL query? P : An SQL query can contain a HAVING clause even if it does not have a GROUP BY clause Q : An SQL query can contain a HAVING clause only if it has a GROUP BY clause R : All attributes used in the GROUP BY clause must appear in the SELECT clause S : Not all attributes used in the GROUP BY clause need to appear in the SELECT clause Show A P and R B P and S C Q and R D Q and S SQL 50 DBMS MCQs with AnswersDiscuss it Question 1 Explanation: According to standard SQL answer should be option (C) which is answer key given by GATE authority. If we talk about different SQL implementations like MySQL, then option (B) is also right. But in question they seem to be talking about standard SQL not about implementation. For example below is a P is correct in most of the implementations. HAVING clause can also be used with aggregate function. If we use a HAVING clause without a GROUP BY clause, the HAVING condition applies to all rows that satisfy the search condition. In other words, all rows that satisfy the search condition make up a single group. See this for more details. S is correct . To verify S, try following queries in SQL. CREATE TABLE temp ( id INT, name VARCHAR(100) ); INSERT INTO temp VALUES (1, "abc"); INSERT INTO temp VALUES (2, "abc"); INSERT INTO temp VALUES (3, "bcd"); INSERT INTO temp VALUES (4, "cde"); SELECT Count(*) FROM temp GROUP BY name; Output: count(*) -------- 2 1 1 Alternative way - Statement (P) "An SQL query can contain a HAVING clause even if it does not have a GROUP BY clause" is correct because Having clause is applied after the aggregation phase and must be used if you want to filter aggregate results and Having doesn't require Group By clause. A HAVING clause without a GROUP BY clause is valid and (arguably) useful syntax in Standard SQL. Consider this example, which is valid Standard SQL: SELECT 'T' AS result FROM Book HAVING MIN(NumberOfPages) < MAX(NumberOfPages); Statement (S) "Not all attributes used in the GROUP BY clause need to appear in the SELECT clause" is correct but if we use Group By clause must, there are limitations on what we can put into the Select clause. Question 2 Table A Id Name Age ---------------- 12 Arun 60 15 Shreya 24 99 Rohit 11 Table B Id Name Age ---------------- 15 Shreya 24 25 Hari 40 98 Rohit 20 99 Rohit 11 Table C Id Phone Area ----------------- 10 2200 02 99 2100 01Consider the above tables A, B and C. How many tuples does the result of the following SQL query contains? SELECT A.id FROM A WHERE A.age > ALL (SELECT B.age FROM B WHERE B. name = "arun") A 4 B 3 C 0 D 1 GATE CS 2012 SQL 50 DBMS MCQs with AnswersDiscuss it Question 2 Explanation: The meaning of “ALL” is the A.Age should be greater than all the values returned by the subquery. There is no entry with name “arun” in table B. So the subquery will return NULL. If a subquery returns NULL, then the condition becomes true for all rows of A (See this for details). So all rows of table A are selected. Source: http://www.geeksforgeeks.org/database-management-system-set-3/ Question 3 Consider a database table T containing two columns X and Y each of type integer. After the creation of the table, one record (X=1, Y=1) is inserted in the table. Let MX and My denote the respective maximum values of X and Y among all records in the table at any point in time. Using MX and MY, new records are inserted in the table 128 times with X and Y values being MX+1, 2*MY+1 respectively. It may be noted that each time after the insertion, values of MX and MY change. What will be the output of the following SQL query after the steps mentioned above are carried out? SELECT Y FROM T WHERE X=7; A 127 B 255 C 129 D 257 GATE CS 2011 SQLDiscuss it Question 3 Explanation: See Question 4 of http://www.geeksforgeeks.org/database-management-systems-set-4/ And question 30 of http://clweb.csa.iisc.ernet.in/rahulsharma/gate2011key.html Question 4 Database table by name Loan_Records is given below. Borrower Bank_Manager Loan_Amount Ramesh Sunderajan 10000.00 Suresh Ramgopal 5000.00 Mahesh Sunderajan 7000.00What is the output of the following SQL query? SELECT Count(*) FROM ( ( SELECT Borrower, Bank_Manager FROM Loan_Records) AS S NATURAL JOIN ( SELECT Bank_Manager, Loan_Amount FROM Loan_Records) AS T ); A 3 B 9 C 5 D 6 GATE CS 2011 SQL 50 DBMS MCQs with AnswersDiscuss it Question 4 Explanation: See Question 3 of http://www.geeksforgeeks.org/database-management-systems-set-4/ Question 5 A relational schema for a train reservation database is given below. Passenger (pid, pname, age) Reservation (pid, class, tid) Table: Passenger pid pname age ----------------- 0 Sachin 65 1 Rahul 66 2 Sourav 67 3 Anil 69 Table : Reservation pid class tid --------------- 0 AC 8200 1 AC 8201 2 SC 8201 5 AC 8203 1 SC 8204 3 AC 8202What pids are returned by the following SQL query for the above instance of the tables? SLECT pid FROM Reservation , WHERE class ‘AC’ AND EXISTS (SELECT * FROM Passenger WHERE age > 65 AND Passenger. pid = Reservation.pid) A 1, 0 B 1, 2 C 1, 3 D 1, 5 GATE CS 2010 SQLDiscuss it Question 5 Explanation: When a subquery uses values from outer query, the subquery is called correlated subquery. The correlated subquery is evaluated once for each row processed by the outer query. The outer query selects 4 entries (with pids as 0, 1, 5, 3) from Reservation table. Out of these selected entries, the subquery returns Non-Null values only for 1 and 3. Question 6 Let R and S be relational schemes such that R={a,b,c} and S={c}. Now consider the following queries on the database: count(*) -------- 2 1 10Which of the above queries are equivalent? A I and II B I and III C II and IV D III and IV GATE-CS-2009 SQLDiscuss it Question 6 Explanation: I and II describe the division operator in Relational Algebra and Tuple Relational Calculus respectively. See Page 3 of this and slide numbers 9,10 of this for more details. Question 7 Consider the following relational schema: count(*) -------- 2 1 11
count(*) -------- 2 1 12
A Find the names of all suppliers who have supplied a non-blue part. B Find the names of all suppliers who have not supplied a non-blue part. C Find the names of all suppliers who have supplied only blue parts. D Find the names of all suppliers who have not supplied only blue parts. E None Discuss it Question 7 Explanation: (D) option matched because given query returns suppliers who have not supplied any blue parts. That means it can include other than blue parts. Question 8 Consider the table employee(empId, name, department, salary) and the two queries Q1 ,Q2 below. Assuming that department 5 has more than one employee, and we want to find the employees who get higher salary than anyone in the department 5, which one of the statements is TRUE for any arbitrary employee table? count(*) -------- 2 1 13 A Q1 is the correct query B Q2 is the correct query C Both Q1 and Q2 produce the same answer. D Neither Q1 nor Q2 is the correct query GATE-CS-2007 SQLDiscuss it Question 8 Explanation: First note that they asked for Anyone (= All) not for Any. count(*) -------- 2 1 14
count(*) -------- 2 1 15
count(*) -------- 2 1 16
Question 9 Given the following statements: count(*) -------- 2 1 17Which one of the following statements is CORRECT? A S1 is TRUE and S2 is FALSE. B Both S1 and S2 are TRUE. C S1 is FALSE and S2 is TRUE. D Both S1 and S2 are FALSE. GATE-CS-2014-(Set-1) SQL 50 DBMS MCQs with AnswersDiscuss it Question 9 Explanation: Check assertions are not sufficient to replace foreign key. Foreign key declaration may have cascade delete which is not possible by just check insertion. Using a check condition we can have the same effect as Foreign key while adding elements to the child table. But when we delete an element from the parent table the referential integrity constraint is no longer valid. So, a check constraint cannot replace a foreign key. So, we cannot replace it with a single check. count(*) -------- 2 1 18
Question 10 Given the following schema: count(*) -------- 2 1 19You want to display the last names and hire dates of all latest hires in their respective departments in the location ID 1700. You issue the following query: SELECT 'T' AS result FROM Book HAVING MIN(NumberOfPages) < MAX(NumberOfPages);0What is the outcome? A It executes but does not give the correct result. B It executes and gives the correct result. C It generates an error because of pairwise comparison. D It generates an error because the GROUP BY clause cannot be used with table joins in a subquery GATE-CS-2014-(Set-1) SQLDiscuss it Question 10 Explanation: The given query uses below inner query. SELECT 'T' AS result FROM Book HAVING MIN(NumberOfPages) < MAX(NumberOfPages);1The inner query produces last max hire-date in every department located at location id 1700. The outer query simply picks all pairs of inner query. Therefore, the query produces correct result. SELECT 'T' AS result FROM Book HAVING MIN(NumberOfPages) < MAX(NumberOfPages);2 What is double data type in SQL?DOUBLE(size, d) A normal-size floating point number. The total number of digits is specified in size. The number of digits after the decimal point is specified in the d parameter. DOUBLE PRECISION(size, d)
Which of the following are SQL data types Mcq?Explanation: SQL Server offers six categories of data types for your use:-exact numeric, Unicode character strings, approximate numeric, Binary strings, Date and time and Character strings. Explanation: Exact numeric data types store numeric values where you wish to specify the precision of the variable.
Which of the following commands in SQL is used to create a table Mcq?Explanation: The CREATE TABLE command is used to create a new table in SQL.
Which type of data can be stored in the database Mcq?5. Which type of data can be stored in the database? Explanation: The reason for creating the database management system was to store large data and these data can be of any form image, text, audio, or video files, etc. DBMS allows the users to store and access the data of any format.
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