What is the difference between partitioning and partition key in a data warehouse?

Partitioning is the technique of dividing a large table into smaller, more manageable pieces based on a specified criterion, such as a column value. The partition key is the column or set of columns that determine which partition a row belongs to. In a data warehouse, you might partition a sales table by date to speed up queries that filter on a specific month. The partition key is the date column used for that division. Partitioning improves query performance by pruning irrelevant partitions and can also aid in data lifecycle management. However, the partition key itself is just the attribute(s) used; you can partition on multiple keys, but the key must be part of the partitioning scheme. In practice, you define the partition key when creating the table (e.g., CREATE TABLE sales PARTITIONED BY (year, month)). The partitioning strategy (range, hash, list) determines how the data is physically stored, but the key remains the same. Thus, partitioning is the overall concept, while the partition key is the specific column(s) that drive that concept.