{"id":19507,"date":"2026-09-23T06:16:53","date_gmt":"2026-09-23T06:16:53","guid":{"rendered":"https:\/\/www.examlabs.com\/certification\/?p=19507"},"modified":"2026-09-23T06:16:53","modified_gmt":"2026-09-23T06:16:53","slug":"comptia-datasys-ds0-001-practice-test-questions-and-exam-dumps-part2-q21-40","status":"publish","type":"post","link":"https:\/\/www.examlabs.com\/certification\/comptia-datasys-ds0-001-practice-test-questions-and-exam-dumps-part2-q21-40\/","title":{"rendered":"CompTIA DataSys+ DS0-001 Practice Test Questions and Exam Dumps Part2 Q21-40"},"content":{"rendered":"

View Full <\/b>CompTIA DataSys+ DS0-001 Exam Dumps<\/b><\/a> and Practice Test Dumps<\/b><\/h2>\n

 <\/p>\n

Question 21.<\/b><\/p>\n

A database administrator wants to prevent duplicate email addresses from being entered into a Users table while still allowing the primary key to remain a separate numeric ID. Which database object is MOST appropriate?<\/b><\/p>\n

    \n
  1. <\/b> Unique constraint<\/span><\/li>\n
  2. <\/b> View<\/span><\/li>\n
  3. <\/b> Trigger log<\/span><\/li>\n
  4. <\/b> Foreign key<\/span><\/li>\n<\/ol>\n

    Correct Answer: 1. Unique constraint<\/b><\/p>\n

    Explanation:<\/b><\/p>\n

    A unique constraint prevents duplicate values from appearing in a specified column or set of columns. In this case, the numeric primary key can continue to identify each row, while a unique constraint on the email column ensures that no two users share the same email address. A foreign key enforces relationships between tables, while views and logging mechanisms do not inherently prevent duplicate values.<\/span><\/p>\n

    Question 22.<\/b><\/p>\n

    Which SQL clause is used to restrict rows returned by a SELECT statement based on a condition?<\/b><\/p>\n

      \n
    1. <\/b> ORDER BY<\/span><\/li>\n
    2. <\/b> WHERE<\/span><\/li>\n
    3. <\/b> GROUP BY<\/span><\/li>\n
    4. <\/b> HAVING<\/span><\/li>\n<\/ol>\n

      Correct Answer: 2. WHERE<\/b><\/p>\n

      Explanation:<\/b><\/p>\n

      The WHERE clause filters rows before they are returned by a query. It can use comparison operators, logical operators, pattern matching, and other conditions. ORDER BY sorts results, GROUP BY organizes rows into groups for aggregation, and HAVING filters groups after aggregation. WHERE is therefore the standard clause used to restrict individual rows based on specified criteria.<\/span><\/p>\n

      Question 23.<\/b><\/p>\n

      A query must return only customers who have placed at least one order. Which type of join is MOST appropriate when joining Customers to Orders?<\/b><\/p>\n

        \n
      1. <\/b> FULL OUTER JOIN<\/span><\/li>\n
      2. <\/b> LEFT JOIN<\/span><\/li>\n
      3. <\/b> INNER JOIN<\/span><\/li>\n
      4. <\/b> CROSS JOIN<\/span><\/li>\n<\/ol>\n

        Correct Answer: 3. INNER JOIN<\/b><\/p>\n

        Explanation:<\/b><\/p>\n

        An INNER JOIN returns only rows that have matching values in both joined tables. If a customer has no related order, that customer is excluded from the result. A LEFT JOIN would include all customers, including those without orders. A FULL OUTER JOIN includes unmatched rows from both tables, while a CROSS JOIN produces combinations of every row from each table.<\/span><\/p>\n

        Question 24.<\/b><\/p>\n

        A database administrator needs to remove all rows from a large staging table quickly while leaving the table structure in place. Which command is MOST appropriate when supported and acceptable for the scenario?<\/b><\/p>\n

          \n
        1. <\/b> DROP<\/span><\/li>\n
        2. <\/b> SELECT<\/span><\/li>\n
        3. <\/b> ALTER<\/span><\/li>\n
        4. <\/b> TRUNCATE**<\/span><\/li>\n<\/ol>\n

          Correct Answer: 4. TRUNCATE<\/b><\/p>\n

          Explanation:<\/b><\/p>\n

          TRUNCATE removes all rows from a table while preserving the table definition. It is often more efficient than deleting rows individually because of how many database systems handle logging and storage deallocation. DROP removes the table object itself. DELETE can also remove rows and allows filtering, but TRUNCATE is commonly preferred when the entire table must be emptied and its limitations are acceptable.<\/span><\/p>\n

          Question 25.<\/b><\/p>\n

          Which normal form primarily requires that repeating groups be removed and that each field contain atomic values?<\/b><\/p>\n

            \n
          1. <\/b> First normal form<\/span><\/li>\n
          2. <\/b> Second normal form<\/span><\/li>\n
          3. <\/b> Third normal form<\/span><\/li>\n
          4. <\/b> Boyce-Codd normal form<\/span><\/li>\n<\/ol>\n

            Correct Answer: 1. First normal form<\/b><\/p>\n

            Explanation:<\/b><\/p>\n

            First normal form requires that table columns contain atomic values and that repeating groups be eliminated. Each row should represent a unique record, and individual fields should not contain multiple repeating values that belong in separate rows or related tables. Higher normal forms address additional dependency issues. First normal form provides the basic structural foundation for normalization.<\/span><\/p>\n

            Question 26.<\/b><\/p>\n

            A table uses a composite primary key consisting of OrderID and ProductID. A column named ProductDescription depends only on ProductID. Which normalization issue is present?<\/b><\/p>\n

              \n
            1. <\/b> Transitive dependency<\/span><\/li>\n
            2. <\/b> Partial dependency<\/span><\/li>\n
            3. <\/b> Referential integrity violation<\/span><\/li>\n
            4. <\/b> Cartesian product<\/span><\/li>\n<\/ol>\n

              Correct Answer: 2. Partial dependency<\/b><\/p>\n

              Explanation:<\/b><\/p>\n

              A partial dependency occurs when a non-key attribute depends on only part of a composite key rather than the whole key. ProductDescription depends only on ProductID, so storing it in a table keyed by both OrderID and ProductID violates second normal form. Moving product-specific attributes into a Products table would reduce redundancy and update anomalies.<\/span><\/p>\n

              Question 27.<\/b><\/p>\n

              A database administrator suspects a slow query is using an inefficient access path. Which database feature should be reviewed FIRST?<\/b><\/p>\n

                \n
              1. <\/b> Backup history<\/span><\/li>\n
              2. <\/b> User password policy<\/span><\/li>\n
              3. <\/b> Query execution plan<\/span><\/li>\n
              4. <\/b> Database name<\/span><\/li>\n<\/ol>\n

                Correct Answer: 3. Query execution plan<\/b><\/p>\n

                Explanation:<\/b><\/p>\n

                A query execution plan shows how the database optimizer intends to retrieve and process data. It can reveal table scans, index usage, join methods, row estimates, sorts, and other potentially expensive operations. Reviewing the plan is a key step in query performance troubleshooting because it helps identify whether indexing, query structure, statistics, or data distribution may be causing inefficiency.<\/span><\/p>\n

                Question 28.<\/b><\/p>\n

                A database index is created on a column that changes very frequently. What is a potential disadvantage?<\/b><\/p>\n

                  \n
                1. <\/b> The table can no longer be queried<\/span><\/li>\n
                2. <\/b> Foreign keys stop working<\/span><\/li>\n
                3. <\/b> Transactions become impossible<\/span><\/li>\n
                4. <\/b> Inserts and updates may require additional index-maintenance work**<\/span><\/li>\n<\/ol>\n

                  Correct Answer: 4. Inserts and updates may require additional index-maintenance work<\/b><\/p>\n

                  Explanation:<\/b><\/p>\n

                  Indexes can improve read performance, but they must be maintained when indexed values are inserted, updated, or deleted. On write-heavy tables, excessive indexing can increase storage use and transaction cost. Effective index design balances read-performance benefits against write overhead. Administrators should create indexes based on actual workload and query patterns rather than indexing every column.<\/span><\/p>\n

                  Question 29.<\/b><\/p>\n

                  Which database security practice BEST supports accountability for privileged administrative activity?<\/b><\/p>\n

                    \n
                  1. <\/b> Use individually assigned administrator accounts with auditing enabled<\/span><\/li>\n
                  2. <\/b> Use one shared root account for all administrators<\/span><\/li>\n
                  3. <\/b> Disable logging to improve performance<\/span><\/li>\n
                  4. <\/b> Allow anonymous administrative connections<\/span><\/li>\n<\/ol>\n

                    Correct Answer: 1. Use individually assigned administrator accounts with auditing enabled<\/b><\/p>\n

                    Explanation:<\/b><\/p>\n

                    Individual administrator identities provide accountability because actions can be associated with specific users. Auditing then records relevant privileged activity for review and investigation. Shared administrative accounts make it difficult to determine who performed a change and weaken nonrepudiation. Least privilege and role-based permissions should also be used to limit administrative access appropriately.<\/span><\/p>\n

                    Question 30.<\/b><\/p>\n

                    A database administrator wants to protect database files and backups if storage media is stolen. Which control is MOST appropriate?<\/b><\/p>\n

                      \n
                    1. <\/b> Data partitioning<\/span><\/li>\n
                    2. <\/b> Encryption at rest<\/span><\/li>\n
                    3. <\/b> Query caching<\/span><\/li>\n
                    4. <\/b> Table normalization<\/span><\/li>\n<\/ol>\n

                      Correct Answer: 2. Encryption at rest<\/b><\/p>\n

                      Explanation:<\/b><\/p>\n

                      Encryption at rest protects stored database files, backups, and other persistent data from unauthorized access if storage devices or backup media are lost or stolen. Encryption in transit protects network communications instead. Effective protection also requires secure key management because encrypted data can still be exposed if encryption keys are improperly stored or accessed.<\/span><\/p>\n

                      Question 31.<\/b><\/p>\n

                      A database administrator needs to grant a reporting user read access to several tables but no ability to modify data. Which permission approach is BEST?<\/b><\/p>\n

                        \n
                      1. <\/b> Grant full database ownership<\/span><\/li>\n
                      2. <\/b> Grant INSERT and UPDATE only<\/span><\/li>\n
                      3. <\/b> Grant SELECT permissions on the required objects<\/span><\/li>\n
                      4. <\/b> Use an unrestricted shared account<\/span><\/li>\n<\/ol>\n

                        Correct Answer: 3. Grant SELECT permissions on the required objects<\/b><\/p>\n

                        Explanation:<\/b><\/p>\n

                        SELECT permission allows users to read data without granting modification rights such as INSERT, UPDATE, or DELETE. This follows least privilege by giving the reporting user only the access necessary to perform the job. Permissions can also be granted through a reporting role or controlled views when additional restrictions on rows or columns are needed.<\/span><\/p>\n

                        Question 32.<\/b><\/p>\n

                        A database server has a recovery point objective of 15 minutes. What does this requirement MOST directly describe?<\/b><\/p>\n

                          \n
                        1. <\/b> The maximum acceptable restore duration<\/span><\/li>\n
                        2. <\/b> The maximum number of users that can be disconnected<\/span><\/li>\n
                        3. <\/b> The maximum database size after recovery<\/span><\/li>\n
                        4. <\/b> The maximum acceptable amount of data loss measured in time**<\/span><\/li>\n<\/ol>\n

                          Correct Answer: 4. The maximum acceptable amount of data loss measured in time<\/b><\/p>\n

                          Explanation:<\/b><\/p>\n

                          Recovery point objective, or RPO, defines how much data loss the organization can tolerate after an incident, measured as a time interval. An RPO of 15 minutes means recovery processes should support restoring data to a point no more than approximately 15 minutes before the disruption. Recovery time objective, or RTO, instead focuses on how quickly service must be restored.<\/span><\/p>\n

                          Question 33.<\/b><\/p>\n

                          Which term describes the maximum acceptable amount of time a database service may remain unavailable after a disruption?<\/b><\/p>\n

                            \n
                          1. <\/b> Recovery time objective<\/span><\/li>\n
                          2. <\/b> Recovery point objective<\/span><\/li>\n
                          3. <\/b> Mean data size<\/span><\/li>\n
                          4. <\/b> Transaction isolation level<\/span><\/li>\n<\/ol>\n

                            Correct Answer: 1. Recovery time objective<\/b><\/p>\n

                            Explanation:<\/b><\/p>\n

                            Recovery time objective, or RTO, defines the target maximum duration for restoring a service after an outage or disaster. It influences recovery architecture, staffing, automation, redundancy, and backup strategy. RPO addresses acceptable data loss, while RTO addresses acceptable downtime. Both objectives should be defined according to business requirements and tested through recovery exercises.<\/span><\/p>\n

                            Question 34.<\/b><\/p>\n

                            A database backup completes successfully every night. What is the BEST way to verify that the backup strategy is actually effective?<\/b><\/p>\n

                              \n
                            1. <\/b> Check only that the backup file exists<\/span><\/li>\n
                            2. <\/b> Perform periodic restore tests and validate recovered data<\/span><\/li>\n
                            3. <\/b> Rename backup files weekly<\/span><\/li>\n
                            4. <\/b> Disable transaction logging during backup<\/span><\/li>\n<\/ol>\n

                              Correct Answer: 2. Perform periodic restore tests and validate recovered data<\/b><\/p>\n

                              Explanation:<\/b><\/p>\n

                              A successful backup job does not guarantee that recovery will work. Restore testing verifies backup integrity, recovery procedures, required credentials, dependencies, and actual recovery time. Recovered data should also be validated to ensure it is usable and complete. Regular restore testing provides confidence that backup procedures will support real incidents rather than merely producing files.<\/span><\/p>\n

                              Question 35.<\/b><\/p>\n

                              A query uses SELECT * against a table containing many large columns, but the application needs only three small fields. What is the BEST optimization?<\/b><\/p>\n

                                \n
                              1. <\/b> Add more tables to the query<\/span><\/li>\n
                              2. <\/b> Disable indexes<\/span><\/li>\n
                              3. <\/b> Select only the required columns<\/span><\/li>\n
                              4. <\/b> Convert all columns to text<\/span><\/li>\n<\/ol>\n

                                Correct Answer: 3. Select only the required columns<\/b><\/p>\n

                                Explanation:<\/b><\/p>\n

                                Selecting only required columns can reduce data transfer, memory usage, I\/O, and processing overhead, especially when a table contains large fields. It also makes query intent clearer and can reduce problems when table schemas change. SELECT * may be convenient for exploration, but application queries should generally retrieve only the data actually needed.<\/span><\/p>\n

                                Question 36.<\/b><\/p>\n

                                A database administrator identifies sessions waiting because two transactions are blocking one another cyclically. What condition has occurred?<\/b><\/p>\n

                                  \n
                                1. <\/b> Replication lag<\/span><\/li>\n
                                2. <\/b> Data masking<\/span><\/li>\n
                                3. <\/b> Index fragmentation<\/span><\/li>\n
                                4. <\/b> Deadlock**<\/span><\/li>\n<\/ol>\n

                                  Correct Answer: 4. Deadlock<\/b><\/p>\n

                                  Explanation:<\/b><\/p>\n

                                  A deadlock occurs when two or more transactions each hold resources the others need, creating a cycle in which none can continue. Database engines typically detect deadlocks and terminate one transaction to break the cycle. Administrators can reduce deadlocks by keeping transactions short, accessing objects in consistent order, and optimizing queries and indexes to minimize lock duration.<\/span><\/p>\n

                                  Question 37.<\/b><\/p>\n

                                  Which practice BEST reduces the likelihood of database deadlocks?<\/b><\/p>\n

                                    \n
                                  1. <\/b> Keep transactions as short as practical and access resources in a consistent order<\/span><\/li>\n
                                  2. <\/b> Increase the duration of every transaction<\/span><\/li>\n
                                  3. <\/b> Remove all indexes<\/span><\/li>\n
                                  4. <\/b> Grant all users administrative privileges<\/span><\/li>\n<\/ol>\n

                                    Correct Answer: 1. Keep transactions as short as practical and access resources in a consistent order<\/b><\/p>\n

                                    Explanation:<\/b><\/p>\n

                                    Short transactions hold locks for less time, reducing the opportunity for blocking and deadlock conditions. Consistent resource-access ordering also helps prevent cyclic waiting between transactions. Appropriate indexing and query optimization can further reduce lock duration. Deadlocks may still occur in complex systems, so applications should also handle transaction retries appropriately where supported.<\/span><\/p>\n

                                    Question 38.<\/b><\/p>\n

                                    A company wants a secondary database server to contain a continuously updated copy of production data for availability purposes. Which capability is MOST relevant?<\/b><\/p>\n

                                      \n
                                    1. <\/b> Normalization<\/span><\/li>\n
                                    2. <\/b> Replication<\/span><\/li>\n
                                    3. <\/b> Tokenization<\/span><\/li>\n
                                    4. <\/b> Compression<\/span><\/li>\n<\/ol>\n

                                      Correct Answer: 2. Replication<\/b><\/p>\n

                                      Explanation:<\/b><\/p>\n

                                      Replication copies data or database changes from one system to another. Depending on the implementation, it can support availability, disaster recovery, geographic distribution, and read scaling. Replication should not automatically be treated as a substitute for backups because accidental deletion or corruption may also be propagated to replicas. Backup and recovery remain separate requirements.<\/span><\/p>\n

                                      Question 39.<\/b><\/p>\n

                                      A database replica is significantly behind the primary server. Which metric should the administrator investigate?<\/b><\/p>\n

                                        \n
                                      1. <\/b> Column count<\/span><\/li>\n
                                      2. <\/b> Primary key length<\/span><\/li>\n
                                      3. <\/b> Replication lag<\/span><\/li>\n
                                      4. <\/b> Number of views<\/span><\/li>\n<\/ol>\n

                                        Correct Answer: 3. Replication lag<\/b><\/p>\n

                                        Explanation:<\/b><\/p>\n

                                        Replication lag measures the delay between changes occurring on the primary database and those changes being applied to a replica. Excessive lag can result from network problems, insufficient resources, heavy write activity, blocked replication processes, or configuration issues. Monitoring lag helps administrators determine whether replicas are sufficiently current for their intended availability or reporting use.<\/span><\/p>\n

                                        Question 40.<\/b><\/p>\n

                                        Which statement BEST describes an effective database monitoring strategy?<\/b><\/p>\n

                                          \n
                                        1. <\/b> Monitor only disk space<\/span><\/li>\n
                                        2. <\/b> Review performance only after users complain<\/span><\/li>\n
                                        3. <\/b> Collect as many metrics as possible without thresholds<\/span><\/li>\n
                                        4. <\/b> Monitor availability, performance, capacity, security, and error indicators with actionable thresholds**<\/span><\/li>\n<\/ol>\n

                                          Correct Answer: 4. Monitor availability, performance, capacity, security, and error indicators with actionable thresholds<\/b><\/p>\n

                                          Explanation:<\/b><\/p>\n

                                          Effective monitoring covers the main areas that affect database reliability and service quality, including resource utilization, query performance, storage capacity, availability, replication, failed jobs, security events, and errors. Alerts should use meaningful thresholds and provide enough context for administrators to act. Monitoring should support trend analysis and proactive capacity planning rather than only reacting after users report problems.<\/span><\/p>\n

                                           <\/p>\n","protected":false},"excerpt":{"rendered":"

                                          View Full CompTIA DataSys+ DS0-001 Exam Dumps and Practice Test Dumps   Question 21. A database administrator wants to prevent duplicate email addresses from being entered into a Users table while still allowing the primary key to remain a separate numeric ID. Which database object is MOST appropriate? Unique constraint View Trigger log Foreign key […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[1648,1647],"tags":[],"_links":{"self":[{"href":"https:\/\/www.examlabs.com\/certification\/wp-json\/wp\/v2\/posts\/19507"}],"collection":[{"href":"https:\/\/www.examlabs.com\/certification\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.examlabs.com\/certification\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.examlabs.com\/certification\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.examlabs.com\/certification\/wp-json\/wp\/v2\/comments?post=19507"}],"version-history":[{"count":1,"href":"https:\/\/www.examlabs.com\/certification\/wp-json\/wp\/v2\/posts\/19507\/revisions"}],"predecessor-version":[{"id":19508,"href":"https:\/\/www.examlabs.com\/certification\/wp-json\/wp\/v2\/posts\/19507\/revisions\/19508"}],"wp:attachment":[{"href":"https:\/\/www.examlabs.com\/certification\/wp-json\/wp\/v2\/media?parent=19507"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.examlabs.com\/certification\/wp-json\/wp\/v2\/categories?post=19507"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.examlabs.com\/certification\/wp-json\/wp\/v2\/tags?post=19507"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}