Column-oriented data storage holds all the values for one attribute contiguously on the storage medium. This arrangement facilitates aggregates but is less efficient when updating existing data.

Column-oriented data storage holds all the values for one attribute contiguously on the storage medium. This contrasts with row-oriented storage where all the values for a single entity are contiguous.

Column-oriented storage facilitates aggregate queries in two ways. First, only the values required are ever recovered from persistent storage (disk). Second, compression is much more effective so fewer bytes must be transferred to convey the same information.