Snowflake Certification Practice Test

What happens to superfluous columns in a query that uses "SELECT * FROM TABLE"?

1. They increase execution time

2. They contribute to data redundancy

3. They reduce data accuracy

4. They have no effect

The correct answer is: They increase execution time

When a query with "SELECT * FROM TABLE" is executed, it retrieves all columns from the specified table. Superfluous columns, which are columns that are not needed for the specific operation or analysis, can indeed increase execution time. This happens because the database system must process and retrieve all of the data, including unnecessary columns, which can lead to additional overhead in terms of memory usage and I/O operations. The inclusion of unnecessary data in the query can slow down performance, especially in large datasets where reading and transferring more data than required takes extra resources and time. Thus, the execution time is directly influenced by the amount of data being retrieved, making this answer accurate in highlighting one of the implications of using "SELECT *". In contrast, the other choices do not directly reflect the consequences of querying superfluous columns in the same way. Data redundancy and accuracy considerations are more related to how the data is structured and stored, rather than the immediate impact of querying more columns than necessary.