Computer Knowledge

Database and SQL

3,929 Questions

Master structured query language commands, database joins, table constraints, and alias generation. This section covers relational database management concepts and query outputs essential for technical aptitude. These technical questions feature prominently in banking IT officer exams and computer knowledge sections.

SQL queries and aliasesDatabase table constraintsDatabase joins and transformationsStored procedures and functions

Database and SQL Questions

Multiple choice technology mainframe

Level 66 used for?

  1. For Renames Clause

  2. For Condition Names

  3. Elementary level item. Cannot be subdivisions of other items (cannot be qualified), nor can they be subdivided themselves.

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Level 66 in COBOL is specifically used for the RENAMES clause, which allows you to regroup existing data items under an alternative name. Level 88 is used for condition names, while level 77 is for independent elementary items. Level 66 cannot serve the purposes described in B or C.

Multiple choice technology databases

Emp table has 10 rows. How many rows will be fetched against the following query? Select 10 from emp where rownum>=2

  1. 2

  2. 8

  3. 10

  4. None of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In Oracle SQL, the ROWNUM pseudo-column is assigned sequentially starting at 1. The condition rownum >= 2 is never met because the first row evaluated is assigned ROWNUM 1, which fails the condition, preventing any subsequent rows from being fetched. Thus, 0 rows are returned.

Multiple choice technology databases

What will be Output of the following query? select length(to_char('9999','999999.99')) from dual

  1. 9

  2. 10

  3. 4

  4. 8
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The format mask '999999.99' in Oracle TO_CHAR specifies 6 digits before decimal (with leading spaces for smaller numbers) and 2 digits after decimal. Converting string '9999' with this mask produces ' 9999.00' which is 10 characters total: 2 leading spaces, 4 digits, decimal point, and 2 decimal digits. The LENGTH function returns 10.

Multiple choice technology databases

If sysdate is ‘17/10/2009’and we run the following query,what will be the Output?

  1. 01/01/10

  2. 01/10/10

  3. 17/10/10

  4. It will throw an error
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The query uses ADD_MONTHS function which adds months to a date. Starting from '17/10/2009', ADD_MONTHS(..., 12) adds 12 months to become '17/10/2010'. The TRUNC function with no arguments truncates to the first day of the month, giving '01/10/2010' (October 1st, 2010). The correct answer is '01/10/10'.

Multiple choice technology databases

You need to modify the STUDENTS table to add a primary key on the STUDENT_ID column. The table is currently empty. Which statement accomplishes this task?

  1. ALTER TABLE students ADD PRIMARY KEY student_id;

  2. ALTER TABLE students ADD CONSTRAINT PRIMARY KEY (student _ id);

  3. ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY (student _ id);

  4. ALTER TABLE students ADD CONSTRAINT stud _ id _pk PRIMARY KEY (student _ id);

  5. ALTER TABLE students MODIFY CONSTRAINT stud _ id _pk PRIMARY KEY (student _ id);
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

To add a primary key with ALTER TABLE, you must use ADD CONSTRAINT with a constraint name and PRIMARY KEY keyword. Option D follows the correct syntax, though note that the column name appears to have unusual spacing. Option A lacks parentheses and constraint name, B lacks the constraint name before PRIMARY KEY, C has potential naming issues, and E uses MODIFY which is not correct for adding constraints.

Multiple choice technology databases

Which syntax turns an existing constraint on?

  1. ALTER TABLE table_name ENABLE constraint_name;

  2. ALTER TABLE table_name STATUS = ENABLE CONSTRAINT constraint _ name;

  3. ALTER TABLE table_name ENABLE CONSTRAINT constraint _ name;

  4. ALTER TABLE table_name TURN ON CONSTRAINT constraint _ name;
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

To turn on an existing constraint, option C is correct:

The correct syntax to turn on an existing constraint is:

C. ALTER TABLE table_name ENABLE CONSTRAINT constraint_name;

Option A is also a valid syntax for enabling a constraint.

Option B is incorrect because there is no "STATUS" option for the ALTER TABLE statement.

Option D is incorrect because there is no "TURN ON" option for the ALTER TABLE statement.

Therefore, the answer is: C. ALTER TABLE table_name ENABLE CONSTRAINT constraint_name;

Multiple choice technology databases

CREATE TABLE statements are not allowed in a trigger.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Triggers execute within the transaction scope of the triggering statement. DDL operations like CREATE TABLE are prohibited because they would require implicit commits that conflict with the trigger's transactional context and could cause rollback issues.

Multiple choice technology

How is a trigger created or replaced if it already exist?

  1. DROP OR REPLACE ‘trigger_name’;

  2. CREATE OR RENAME TRIGGER ‘trigger_name’;

  3. CREATE OR REPLACE TRIGGER ‘trigger_name’;

  4. CREATE OR RECREATE TRIGGER ‘trigger_name’;
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The SQL syntax for creating a new trigger or replacing an existing one is CREATE OR REPLACE TRIGGER followed by the trigger name. This allows modifying a trigger without first dropping it.

Multiple choice technology platforms and products

Which type of join is not available in join component?

  1. Inner Join

  2. Explicit Join

  3. Full Outer join

  4. None of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The Join component in Ab Initio supports all standard join types: Inner Join, Full Outer Join, Left Outer Join, and Right Outer Join. 'Explicit Join' is not a standard join category, and since all valid join types ARE available, 'None of the above' is correct.

Multiple choice technology programming languages

The WHERE statement does not perform automatic conversions(character/numeric) in comparisons :True or False?

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The WHERE statement does NOT perform automatic type conversion - if you compare character and numeric values, SAS will produce an error. Unlike some other SAS statements that attempt implicit conversions, WHERE requires compatible types or explicit conversion functions.

Multiple choice technology web technology

Extracts from a database a single record that matches the specified criteria

  1. GETDATA

  2. GETDB

  3. DGET

  4. None of the Above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

DGET is a database function that extracts a single record from a database that matches specified criteria. Unlike other database functions that perform calculations or aggregations, DGET retrieves actual field values from one matching record. It returns an error if multiple records match the criteria.