Among factors impacting query processing, which has greater impact: the overall size of the tables being queried or the number of rows?

• A. Number of Rows
• B. Both Are Equal
• C. Neither Affects Performance
• D. Overall Table Size Has Greater Impact

Answer: (D)

In query processing, what really drives performance is how much data the system must read and process, i.e., the amount of data scanned in bytes. The overall size of the table in bytes sets the potential amount of data that could be touched during a query. While having many rows can influence work like joins or sorts, the per-row width and compression determine how many bytes those rows actually become on disk. You can have a large number of narrow, highly compressible rows or a small number of very wide rows, and the data scanned can vary accordingly. So, increasing the table’s total size generally leads to more data to read and longer runtimes, making the overall table size the greater impact on query processing.