How do you optimize a query that takes too long to execute?
- Use indexes, optimize joins, and minimize the use of wildcard characters in WHERE clauses.
- Increase the complexity of the query to obtain more detailed results.
- Add more tables to the FROM clause for a comprehensive dataset.
- Include redundant columns in the SELECT statement.
To optimize a slow query, you should use indexes, optimize joins, and minimize the use of wildcard characters in WHERE clauses. These practices help the database engine retrieve and process data more efficiently. Options 2, 3, and 4 are counterproductive and would likely worsen the performance.
_______ is an open-source tool for big data visualization which works particularly well with Hadoop data.
- Apache Superset
- Power BI
- QlikView
- Tableau
Apache Superset is an open-source tool designed for big data visualization. It integrates well with Hadoop data, providing a platform for creating insightful and interactive visualizations for large datasets. Tableau, Power BI, and QlikView are also popular visualization tools but may not be as tailored for Hadoop integration as Apache Superset.
What is the equivalent of SQL's JOIN operation in dplyr for merging two datasets?
- combine()
- inner_join()
- join()
- merge()
In dplyr, the inner_join() function is equivalent to SQL's JOIN operation. It merges two datasets based on matching keys, similar to the merge() function in Pandas. combine() and join() have different functionalities and are not direct equivalents to SQL JOIN.
What is the primary function of the SELECT statement in SQL?
- Create a new table
- Delete records from a table
- Retrieve data from one or more tables
- Update data in a table
The primary function of the SELECT statement in SQL is to retrieve data from one or more tables. It allows you to specify the columns you want to retrieve and apply conditions to filter the results.
For sequential pattern mining, the _______ algorithm is widely used to identify frequent sequences in data sets.
- Apriori
- DBSCAN
- FP-Growth
- K-Means
The FP-Growth algorithm is widely used for sequential pattern mining. It efficiently identifies frequent sequences in data sets by employing a tree structure to represent the relationships between sequential patterns.
For a dashboard handling large datasets, what strategy is crucial for maintaining performance and speed?
- Data Compression
- Data Duplication
- Data Normalization
- Indexing
Indexing is crucial for maintaining performance and speed in a dashboard handling large datasets. It allows for efficient data retrieval by creating a data structure that accelerates the retrieval of rows based on the values in one or more columns.
For recursive queries in SQL, the ________ keyword is often used.
- CONNECT BY
- HIERARCHY
- RECURSIVE
- WITH
The WITH keyword, also known as Common Table Expressions (CTE), is often used in SQL for handling recursive queries. It allows you to define temporary result sets that can be referenced within the context of the main query.
When designing a dashboard for an educational institution, what features should be included to track student performance and engagement effectively?
- Aesthetic background images
- Static tables of test scores
- Student progress timelines and achievement badges
- Word clouds of student feedback
Student progress timelines and achievement badges are effective features for tracking student performance and engagement in an educational dashboard. They provide a visual representation of progress and accomplishments, fostering motivation. Word clouds and static tables may not capture the dynamic nature of student engagement effectively, and aesthetic background images are more for decoration than analytical value.
To change the structure of a database table, the _______ SQL statement is used.
- ALTER
- CHANGE
- MODIFY
- UPDATE
The ALTER SQL statement is used to modify the structure of a database table. It can be used to add, delete, or modify columns, as well as change data types or constraints.
In a situation where data consistency is crucial, and you have multiple related update operations, how would you manage these operations in SQL?
- Apply triggers
- Use indexes
- Use transactions
- Utilize stored procedures
To ensure data consistency in situations involving multiple related update operations, transactions are used in SQL. Transactions allow you to group multiple SQL statements into a single, atomic operation, ensuring that all changes are applied or none at all.