CompTIA DS0-001 Exam Actual Questions

The constraint that is used to enforce referential integrity is foreign key. A foreign key is a column or a set of columns in a table that references the primary key of another table. A primary key is a column or a set of columns in a table that uniquely identifies each row in the table. Referential integrity is a rule that ensures that the values in the foreign key column match the values in the primary key column of the referenced table. Referential integrity helps maintain the consistency and accuracy of the data across related tables. The other options are either different types of constraints or not related to referential integrity at all. For example, a surrogate key is a column that is artificially generated to serve as a primary key, such as an auto-increment number or a GUID (Globally Unique Identifier); a unique key is a column or a set of columns in a table that uniquely identifies each row in the table, but it can have null values unlike a primary key; there is no such constraint as TID.Reference:CompTIA DataSys+ Course Outline, Domain 1.0 Database Fundamentals, Objective 1.2 Given a scenario, execute database tasks using scripting and programming languages.

The NF (normal form) that is considered the most preferable for relational database design is 3 NF. 3 NF, or Third Normal Form, is a level of normalization that organizes data into tables and columns to reduce redundancy and improve consistency. Normalization is a process that applies a set of rules or criteria to eliminate or minimize the anomalies or problems that may arise from inserting, updating, or deleting data in a database. 3 NF is achieved when a table satisfies the following conditions: - It is in 2 NF (Second Normal Form), which means that every non-key column depends on the whole primary key and not on any subset of it - It has no transitive dependencies, which means that every non-key column depends directly on the primary key and not on any other non-key column 3 NF is considered the most preferable for relational database design because it ensures that each table has only one purpose or theme and that each column has only one value or meaning. This helps avoid data duplication, inconsistency, and update anomalies. The other options are either lower or higher levels of normalization that are either less preferable or less practical for relational database design. For example, 1 NF (First Normal Form) is the lowest level of normalization that requires each column to have atomic values and each row to have a unique identifier; 4 NF (Fourth Normal Form) is a higher level of normalization that requires each table to have no multi-valued dependencies, which means that there are no columns that can have more than one value for the same primary key value; 2 NF (Second Normal Form) is an intermediate level of normalization that requires each non-key column to depend on the whole primary key and not on any subset of it.Reference:CompTIA DataSys+ Course Outline, Domain 1.0 Database Fundamentals, Objective 1.2 Given a scenario, execute database tasks using scripting and programming languages.

The index that stores records in a tabular format is columnstore. A columnstore index is a type of index that stores and compresses data by columns rather than by rows. A columnstore index can improve the performance and efficiency of queries that perform aggregations, calculations, or analysis on large amounts of data, such as data warehouse or business intelligence applications. A columnstore index can also reduce the storage space required for data by applying various compression techniques, such as dictionary encoding, run-length encoding, bit packing, etc. The other options are either different types of indexes or not related to indexes at all. For example, a non-clustered index is a type of index that stores the values of one or more columns in a sorted order along with pointers to the corresponding rows in the table; a unique index is a type of index that enforces uniqueness on one or more columns in a table; a secondary index is an alternative term for a non-clustered index.Reference:CompTIA DataSys+ Course Outline, Domain 3.0 Database Management and Maintenance, Objective 3.1 Given a scenario, perform common database maintenance tasks.

The resource that is the best way to lock rows in SQL Server is RID. RID, or Row IDentifier, is an attribute that uniquely identifies each row in a heap table in SQL Server. A heap table is a table that does not have a clustered index, which means that the rows are not stored in any particular order. A RID consists of the file number, page number, and slot number of the row in the database. A RID can be used to lock rows in SQL Server to prevent concurrent access or modification by other transactions or users. A RID lock is a type of lock that locks a single row using its RID. A RID lock can be applied using theHOLDLOCKorXLOCKhints in aSELECTstatement. The other options are either not related or not effective for this purpose. For example, TID, or Transaction IDentifier, is an attribute that uniquely identifies each transaction in a database; SID, or Security IDentifier, is an attribute that uniquely identifies each user or group in a Windows system; PID, or Process IDentifier, is an attribute that uniquely identifies each process in an operating system.Reference:CompTIA DataSys+ Course Outline, Domain 3.0 Database Management and Maintenance, Objective 3.3 Given a scenario, implement database concurrency methods.

The command that is part of DDL is CREATE. CREATE is a SQL command that belongs to the category of DDL, or Data Definition Language. DDL is a subset of SQL commands that are used to define or modify the structure or schema of a database, such as tables, columns, constraints, indexes, views, etc. CREATE is a DDL command that is used to create a new object in a database, such as a table, column, constraint, index, view, etc. For example, the following statement uses the CREATE command to create a new table called employee with four columns:

CREATE TABLE employee (

emp_id INT PRIMARY KEY,

emp_name VARCHAR(50) NOT NULL,

emp_dept VARCHAR(20),

emp_salary DECIMAL(10,2)

);

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The other options are either part of different categories of SQL commands or not SQL commands at all. For example, UPDATE is a SQL command that belongs to the category of DML, or Data Manipulation Language. DML is a subset of SQL commands that are used to manipulate or modify the data or content of a database, such as inserting, updating, deleting, or selecting data. GRANT is a SQL command that belongs to the category of DCL, or Data Control Language. DCL is a subset of SQL commands that are used to control or manage the access or permissions of users or roles on a database, such as granting or revoking privileges or roles. INSERT is a SQL command that belongs to the category of DML, or Data Manipulation Language. INSERT is a DML command that is used to insert new data into a table.Reference:CompTIA DataSys+ Course Outline, Domain 1.0 Database Fundamentals, Objective 1.2 Given a scenario, execute database tasks using scripting and programming languages.