docs-v2/content/influxdb/v2/reference/key-concepts/data-schema.md

title	description	aliases	weight	menu	influxdb/v2/tags
InfluxDB data schema	InfluxDB uses a tabular data schema for displaying raw data in Data Explorer and for returning query results in annotated CSV syntax.	/influxdb/v2/reference/key-concepts/table-structure	103	influxdb_v2 parent name Key concepts Data schema	key concepts

InfluxDB data elements are stored in time-structured merge tree (TSM) and time series index (TSI) files to efficiently compact stored data.

InfluxDB also provides a tabular data schema that includes the following:

• Annotation rows
• Header row
• Data rows
• Other columns
• Group keys

The tabular data schema is used for the following:

• To view raw data when exploring metrics with InfluxDB
• To return query results in annotated CSV syntax

Annotation rows

Annotation rows describe column properties, for example:

• #group
• #datatype
• #default

Header row

The header row defines column labels that describe data in each column, for example:

• table
• _time
• _value
• _field
• _measurement
• tag key names (without underscore prefix): tag-1, tag-2

Data rows

Each data row contains the data specified in the header row for one point.

Other columns

In addition to the columns in each data row (specified in the header row), the following columns are optional:

• annotation
• result
• table

Group keys

Determine the contents of output tables in Flux by grouping records that share common values in specified columns. Learn more about grouping your data with Flux.