Glossary · Database

Data Dictionary

A data dictionary is a centralized reference that documents every table and column in a database–what it contains, what its values mean, and how it should be used.

A schema tells you a column is called "status" and holds integers; a data dictionary tells you that 1 means trial, 2 means active, and 3 means churned-but-recoverable. That institutional knowledge usually lives in the heads of two engineers, which is why new analysts take weeks to write trustworthy queries. A maintained data dictionary makes the database legible to humans–and increasingly to AI, since the same descriptions that help a new hire also dramatically improve an AI's ability to translate business questions into correct SQL.

Fig — every answer ships with the tables, rows and SQL behind it.