Skipping Before Scanning
The fastest data to read is data you never touch. Query pruning uses lightweight metadata to decide whole blocks of storage cannot match a filter, so the engine skips them entirely.
Zone Maps
A zone map stores the min and max value of a column for each block of rows. If a query asks for amount greater than 500 and a block has a max of 200, the block cannot contain a match and is skipped without reading it.
Why Order Matters
Pruning works best when data is sorted or clustered, because then each block covers a narrow value range. Random data gives wide ranges per block, so few blocks can be ruled out and pruning barely helps.
Key idea
Zone maps store per block min and max values so the engine skips blocks that cannot match a filter, and clustering data tightens those ranges to make pruning far more effective.