Recent questions and answers in Databases

​​​​​Which of the following file organizations is/are $\text{I/O}$ efficient for the scan operation in $\text{DBMS}$?SortedHeapUnclustered tree indexUnclustered hash inde...

Consider,CREATE TABLE zoomers ( lecture_id INTEGER PRIMARY KEY, week INTEGER NOT NULL, topic VARCHAR(30) NOT NULL, num_thanks INTEGER, poppin_chat BOOLEAN );Assume,intege...

Consider the following statement:In fixed-length records, a character field of type $\mathrm{CHAR}$ is not allowed.Enter $1$ if the statement is true and $0$ if it is fal...

Consider,Universities( name TEXT, abbrev CHAR(3), addr TEXT, zip CHAR(5), phone TEXT, enrolled INTEGER )Assume,record header = $4$ bytes, integer = $4$ bytes, a $\mathrm{...

Which of the following are benefits of using a record header for variable-length records?Delimiter characters between fields are not required. It always uses equal or les...

Consider:CREATE TABLE products ( id INTEGER PRIMARY KEY, stock INTEGER NOT NULL, price INTEGER NOT NULL, name VARCHAR(10) NOT NULL, category CHAR(6) NOT NULL, serial_numb...

A university placement center maintains a relational database of companies that interview students on campus and make job offers to those successful in the interview. The...

On a relation named $\text{Loan}$ of a bank:\[\begin{array}{|c|}\hline\textbf{Loan} \\\hline\begin{array}{c|c|c}\textbf{loan_number} & \textbf{branch_name} & \textbf{amou...

A disk has cylinders $:0\mathrm{\ to\ }999$The current head position is $:253$Pending requests are:$$98,\ 120,\ 283,\ 137,\ 352,\ 414,\ 29,\ 665,\ 867,\ 919,\ 534,\ 737$$...

The designer of an operating system noticed, after performance measurements, that the system presented disk access problems, with a very high average waiting time. Select...

A disk contains $\mathbf{400}$ tracks, numbered : $0\mathrm{\ to\ }399$A request at track $200$ has just been completed. The head is now moving toward smaller track numbe...

The disk head is currently at track : $105$ and is moving toward larger track numbers.Pending requests are:$$35,\ 45,\ 12,\ 68,\ 110,\ 180,\ 170,\ 195$$If SCAN scheduling...

A magnetic-disk head is currently at cylinder : $100$Pending requests are:$120,\ 90,\ 70,\ 80,\ 140,\ 110,\ 60$The scheduling method follows these rules:requests may be r...

Which of the following statements about magnetic-disk arm scheduling is incorrect?FCFS handles requests according to arrival order and is considered fair, although it gen...

Consider the following statement:If disk requests are scheduled using SSTF, the seek time will increase compared with FCFS. Furthermore, the elevator algorithm is not rec...

A disk has $200$ tracks numbered $0$ through $199$.The disk head is currently at track $:184$Disk requests arrive for:$184,\ 187,\ 176,\ 182,\ 199$If SSTF scheduling is u...

Suppose a disk repeatedly services requests for one particular track while requests for other tracks remain unserved. This phenomenon is called disk-arm sticking.Which of...

Which disk scheduling algorithm selects the pending request requiring the smallest movement of the disk arm from its current position, thereby choosing the minimum seek t...

A computer scientist wants to determine the time required to read an entire magnetic disk.Assume:$2400$ cylinders $6$ tracks per cylinder $32$ sectors per track one compl...

Which of the following statements about magnetic disk storage is incorrect?The formatted capacity of a disk is smaller than its unformatted capacity. A sector contains in...

A disk has:rotational speed $=7200\ \mathrm{rpm}$ average seek time $=8\ \mathrm{ms}$ sectors per track $=1000$Approximately how much time is required, on average, to acc...

A magnetic disk rotates at $4200\ \mathrm{rpm}$. Its average positioning time is $5\ \mathrm{ms}$The average waiting time is defined as:$$\mathrm{Average\ positioning\ ti...

A magnetic disk has a sector size of $\mathbf{512}$ bytes. Each sector is identified by a $\mathbf{28}$-bit sector number.What is the maximum disk capacity that can be ma...

Consider:$\mathrm{DEPT(dname,\ location)}$$\mathrm{STUDENT(name,\ regno,\ gpa,\ level,\ dept)}$$\mathrm{COURSE(cno,\ cname,\ dept)}$$\mathrm{TAKE(regno,\ cno)}$and the SQ...

Consider relations $\mathrm{R}$ and $\mathrm{S}$.Five SQL commands are shown:Command I :SELECT R.* FROM R WHERE EXISTS (SELECT * FROM S WHERE R.a = S.c);Command II :SELEC...

Consider:$\mathrm{Observation(Seq,\ BirdName,\ ObservationCount)}$with primary key:$\mathrm{(Seq,\ BirdName)}$The following statement inserts combinations of sequence num...

Relation $\mathrm{R1(A,B)}$ contains:$$\begin{array}{|c|c|} \hline \mathrm{A} & \mathrm{B} \\ \hline 1 & 2 \\ 2 & 2 \\ 3 & 3 \\ 4 & 3 \\ 4 & 2 \\ 4 & 1 \\ 5 & 0 \\ \hline...

Consider the relation:$$\begin{array}{|c|c|c|} \hline \mathrm{EmployeeCode} & \mathrm{Supervisor} & \mathrm{Name} \\ \hline \mathrm{S001} & \mathrm{NULL} & \mathrm{A} \\ ...

Relevant relations are:$\mathrm{BUILDING(BID,\ BName,\ Address)}$$\mathrm{IN\_BUILDING(EID,\ BID)}$Which of the following queries correctly find the names of buildings wh...

Consider relations:$\mathrm{Product}$$\mathrm{Inventory}$where the underlined attributes in the original examination are primary keys.The following query returns product ...

Consider,SELECT DISTINCT TBL1.COL1 FROM TBL1 WHERE COL1 IN (SELECT COL1 FROM TBL2);Which SQL statement produces the same result?SELECT DISTINCT TBL1.COL1 FROM TBL1 UNION ...

Consider the relation $R(a,b)$. The relation may contain duplicate tuples.Which of the following queries are guaranteed not to contain duplicate tuples, regardless of the...

Three relations with the same schema are maintained for three regions:$\mathrm{TokyoProduct}$, $\mathrm{NagoyaProduct}$, and $\mathrm{OsakaProduct}$$\mathrm{ProductNo}$ i...