Practice by Category & Subject

Repeatable Read isolation ensures transactions see consistent snapshot throughout transaction. It prevents non-repeatable reads and phantom reads through MVCC. Serialization errors can occur requiring retry logic. Understanding Repeatable Read enables stronger consistency requirements.

Question 2 Easy Mcq

✓ Correct ✗ Incorrect

What is the default variable for the PROMPT3?

>>> '

>> '

%/%R%# '

Explanation:

Partitioning divides large tables into smaller pieces. Methods include range, list, and hash partitioning. Partitioning improves performance and maintenance. Understanding partitioning enables scaling large tables.

Question 3 Easy Mcq

✓ Correct ✗ Incorrect

What is the default location of the standard elog?

/var/log/messages

$PGDATA/serverlog

Any of the above

None of the above

Explanation:

Declarative partitioning uses PARTITION BY clause defining partitioning strategy. Partitions are created as child tables. Understanding declarative partitioning simplifies partition management.

Question 4 Easy Mcq

✓ Correct ✗ Incorrect

True or false: With table inheritance child tables inherit primary and foreign key definitions from their parents

false

true

Explanation:

False. With table inheritance in PostgreSQL, child tables do NOT inherit primary key, foreign key, or unique constraints from parent tables. Children inherit columns and check constraints but constraints requiring indexes aren't inherited. This design prevents constraint conflicts across inheritance hierarchies. Understanding inheritance limitations ensures proper constraint definition in child tables.

Question 5 Easy Mcq

✓ Correct ✗ Incorrect

What is the difference between tokens and lexemes?

Tokens are always in upper case

Lexemes are normalized

A lexeme is a string while a token is an integer

Lexemes are always in upper case

Explanation:

JSONB operators enable efficient JSON querying including containment (@>), existence (?), and path extraction (->). GIN indexes optimize JSONB queries. Understanding JSONB enables document database patterns.

Question 6 Easy Mcq

✓ Correct ✗ Incorrect

What is "index bloat"?

Indexing too many tables, resulting in inefficient database performance.

No-longer-needed keys in an index aren't reclaimed, therefore increasing space required to store an index, as well as time it takes to scan.

Indexing inefficiently, like choosing to index timestamps in a table.

Index filling up with keys.

Explanation:

Persistent objects store class instances in databases using SAP persistence service. They enable object-oriented data persistence. Understanding persistent objects enables OO database programming.

Question 7 Easy Mcq

✓ Correct ✗ Incorrect

On a UNIX system, what is the best way to prevent all non-local connections to the postmaster?

Using ipfilter

Using UNIX sockets

Using TCP port 0

Using an empty pg_hba.conf

Explanation:

Advisory locks are application-level locks managed by PostgreSQL but interpreted by application. They enable coordinating across sessions without locking database objects. Understanding advisory locks enables custom locking strategies.

Question 8 Easy Mcq

✓ Correct ✗ Incorrect

True or false: When a table is created which uses a table name as a column type, not null constraints on the column type's table definition are honored by the including table.

true

false

Explanation:

OData services provide RESTful access to SAP data. Gateway framework exposes OData services. Understanding OData enables modern API development.

Question 9 Easy Mcq

✓ Correct ✗ Incorrect

What is the name of the special time input with value 00:00:00.00 UTC?

zero

noon

midnight

allballs

Explanation:

Constraints enforce data integrity including PRIMARY KEY, FOREIGN KEY, UNIQUE, CHECK, NOT NULL, and EXCLUSION. They prevent invalid data entry. Understanding constraints ensures data quality and business rule enforcement.

Question 10 Easy Mcq

✓ Correct ✗ Incorrect

What is the command used to import a backup made with pg_dumpall > file.dmp?

pg_restore file.dmp

psql -f file.dmp

pg_restoreall file.dmp

postgre --restore -f file.dmp

Explanation:

Common Table Expressions (CTEs) define temporary result sets using WITH. They improve query readability and enable recursion. CTEs make complex queries maintainable. Understanding CTEs enables building complex queries clearly.

Question 11 Easy Mcq

✓ Correct ✗ Incorrect

If entity x is existence-dependent on entity y, then what is x called?

Dominant entity

Subordinate entity

Primary entity

Secondary entity

Explanation:

NOT NULL constraints prevent NULL values in columns. They ensure required data presence. Understanding NOT NULL enforces data completeness.

Question 12 Easy Mcq

✓ Correct ✗ Incorrect

Data validation can be implemented at the definition stage through:

Check constraints with specified values

Referential constraints, by creating a foreign key for another table

Default value of a column

Null constraints

Explanation:

EXCEPT returns rows in first query not in second. It finds differences between result sets. Understanding EXCEPT enables identifying unique rows in one dataset.

Question 13 Easy Mcq

✓ Correct ✗ Incorrect

What is wrong in this query:Select * from Orders where OrderID=(select OrderID from OrderItems where ItemQty>50)

In a sub query, * should be used instead of OrderID

The sub query can return more than one row, so, = should be replaced with in

The sub query should be used first

None of the above

Explanation:

The query has a subquery that can return multiple values but uses = operator which expects single value. The correct operator should be IN when subquery returns multiple rows. The query should be: SELECT * FROM Orders WHERE OrderID IN (SELECT OrderID FROM OrderItems WHERE...). Understanding scalar vs. set operators prevents SQL errors.

Question 14 Easy Mcq

✓ Correct ✗ Incorrect

What is the difference between to_tsvector() and ::tsvector ?

to_tsvector () normalizes the string while ::tsvector does not

to_tsvector () can be used in select statements, while ::tsvector cannot

They are equivalent

None of the above

Explanation:

Stored procedures are functions that can commit/rollback transactions. They use CALL statement. Procedures enable transaction control within routines. Understanding procedures enables complex transaction logic.

Question 15 Easy Mcq

✓ Correct ✗ Incorrect

What is the wrapper around the SQL command CREATE DATABASE?

newdb

add_DB

NEW_DB

createdb

Explanation:

Table maintenance generator (SE54) creates maintenance dialogs for tables and views. It generates screens and function modules automatically. Understanding TMG enables quick maintenance dialog creation.

Question 16 Easy Mcq

✓ Correct ✗ Incorrect

The basic psql command to list tables is?

\do

\dT

\dt

Explanation:

Table controls display and edit internal table data in screens. They provide grid-like interfaces. Understanding table controls enables tabular data editing.

Question 17 Easy Mcq

✓ Correct ✗ Incorrect

When using LIKE to compare strings, what is the wildcard operator (operator which matches zero or more characters)?

Explanation:

ANALYZE collects statistics about table contents used by query planner. Accurate statistics enable optimal query plans. ANALYZE runs automatically with autovacuum but can be run manually. Understanding ANALYZE ensures efficient query execution through proper statistics.

Question 18 Easy Mcq

✓ Correct ✗ Incorrect

What is the first step for manually installing PL/pgSQL in PostgreSQL?

Use 'CREATE FUNCTION' to create the procedural call handler

Use 'CREATE LANGUAGE' SQL command

Either one of the above can be used

Explanation:

INNER JOIN returns only matching rows from both tables based on join condition. It's most common join type. Non-matching rows are excluded. Understanding INNER JOIN enables combining related data from multiple tables.

Question 19 Easy Mcq

✓ Correct ✗ Incorrect

What is the ~ operator?

POSIX regular expression match operator

XOR operator

NOT operator

Home directory ENV variable

Explanation:

#N/A

Question 20 Easy Mcq

✓ Correct ✗ Incorrect

What is the difference between DO 'some code...' and EXECUTE 'some code...' statements?

DO prepares a statement and EXECUTE executes it

No difference - they both need a preparation for execution

No difference - they both can execute a code without preparation

DO lets you execute some plPgSql code without saving it to database and EXECUTE lets you execute DDL or DML only

Explanation:

ALE (Application Link Enabling) distributes applications and data across SAP systems using IDOCs and BAPIs. It enables distributed landscapes. Understanding ALE enables system integration.

Question 21 Easy Mcq

✓ Correct ✗ Incorrect

What is the effect of turning fsync off in postgresql.conf?

File synchronization will be deactivated

fsync is not a valid configuration option

PostgreSQL will not enforce write ahead log flush

It will turn off fast synchronization

Explanation:

Hash indexes support only equality comparisons using = operator. They're smaller than B-trees for certain data but historically had limitations including lack of WAL logging. Modern PostgreSQL versions improved hash indexes but B-trees remain preferred for most cases. Understanding hash index limitations guides appropriate use.

Question 22 Easy Mcq

✓ Correct ✗ Incorrect

What is true regarding file system backup?

It can only be used to backup the whole database

The database must be running for the backup to take place

To restore a file system backup, pg_restore should be used

None of the above

Explanation:

Triggers execute functions automatically on INSERT, UPDATE, DELETE, or TRUNCATE. They can be BEFORE, AFTER, or INSTEAD OF. Triggers enable auditing, validation, and cascading changes. Understanding triggers enables reactive database logic.

Question 23 Easy Mcq

✓ Correct ✗ Incorrect

What is a TOAST file?

A file containining transactions which were unsuccessfully completed due to errors.

A list of clients not allowed to connect to the database.

A file containing values too wide to fit comfortably in the main table

A file storing data that was unable to be written to the database, and will be expunged once the server shuts down.

Explanation:

CDS (Core Data Services) define semantic data models using DDL. CDS views enable advanced data modeling. Understanding CDS enables modern ABAP development on HANA.

Question 24 Easy Mcq

✓ Correct ✗ Incorrect

What is a cluster?

A group of users

A group of indexes

A method that reorganizes the table on the disc to increase performance

A compressed datafile

Explanation:

Logical replication replicates specific tables/changes selectively. It enables database upgrades and data distribution. Understanding logical replication enables flexible replication scenarios.

Question 25 Easy Mcq

✓ Correct ✗ Incorrect

What is the default ordering when ORDER BY is not specified?

By ID

By insertion date

By name

The ordering is unknown if not specified

Explanation:

CLUSTER physically reorders table data according to index order, improving sequential access performance. It requires exclusive lock and isn't maintained automatically. CLUSTER is expensive but benefits range scans. Understanding cluster enables optimizing specific access patterns.

Question 26 Easy Mcq

✓ Correct ✗ Incorrect

What is a rollback of transactions normally used for?

To recover from the transaction failure

To update the transaction

To retrieve old records

None of the above

Explanation:

Database concepts include normalization, indexing, transactions, and optimization. Understanding these fundamentals enables designing efficient, reliable database systems. Proper database design considers performance, integrity, scalability, and maintainability requirements. Each concept serves specific purposes in ensuring database quality and effectiveness.

Question 27 Easy Mcq

✓ Correct ✗ Incorrect

What is the well known port number for the postgresql database service?

5000

541

5432

Explanation:

Covering indexes include all columns needed by queries, enabling index-only scans without accessing table data. They're created using INCLUDE clause for non-key columns. Covering indexes dramatically improve query performance by avoiding table access. Understanding covering indexes enables maximum query optimization.

Question 28 Easy Mcq

✓ Correct ✗ Incorrect

What is the correct order of clauses in the select statement?1 select2 order by3 where4 having5 group by

1,2,3,4,5

1,3,5,4,2

1,3,5,2,4

1,3,2,5,4

Explanation:

The correct order of SELECT statement clauses is: 1-SELECT 2-FROM 3-WHERE 4-GROUP BY 5-HAVING 6-ORDER BY. This order represents logical processing flow: select columns, from tables, filter rows, group results, filter groups, order output. Understanding clause order prevents syntax errors and ensures proper query construction.

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