Start with the question
A table, dashboard or model is useful only when its grain, audience and decision are explicit.
Data Glossary: 100+ Analytics, SQL and Data Science Terms
Learn 100+ data terms across analytics, SQL, databases, statistics, data science, pipelines, warehouses and big-data architecture with clear explanations.
A USEFUL MENTAL MODELLearn the language.
Learn the language.
Understand the system.
Good data work depends on shared definitions. A metric can be technically correct yet misleading if its grain, source or business meaning is unclear. This glossary connects database structure, analytical reasoning, statistics and modern data platforms so learners can move from vocabulary to trustworthy decisions.
Quality is part of analysis
Missingness, duplication, lineage and freshness influence every result; documenting them is analytical work.
Architecture serves access
Warehouses, lakes and streaming platforms solve different combinations of history, scale, latency and governance.
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Every term now connects
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108 termsClear definitions · Relevant learning paths
A/B test
A controlled experiment comparing two variants against a predefined outcome metric.
ACID transaction
A database transaction that preserves atomicity, consistency, isolation and durability.
Aggregation
The calculation of summaries such as totals, averages or counts across groups of records.
Analytical query
A query designed to compare, group or summarise data for investigation and decision-making.
Approximate query
A query that trades exactness for faster answers on large datasets.
Batch processing
Processing a collected group of records together on a schedule or trigger.
Big data
Data whose scale, speed or variety requires distributed storage, processing or specialised architecture.
Business intelligence (BI)
Tools and practices that turn organisational data into reports, dashboards and decision support.
Cardinality
The number of distinct values in a field or relationships associated with an entity.
Column
A named field that stores one type or meaning of value across table rows.
Columnar database
A database that stores values by column to accelerate analytical scans and compression.
Common table expression (CTE)
A named temporary result used to structure a larger SQL statement.
Correlation
A measure of how strongly two variables move together, without by itself proving causation.
Dashboard
A structured visual display of metrics and patterns created for a defined audience and decision.
Data analytics
The practice of transforming data into metrics, patterns and recommendations that support decisions.
Data catalog
A searchable inventory describing available datasets, ownership, meaning, quality and access.
Data cleaning
The detection and treatment of missing, duplicated, inconsistent or invalid data.
Data contract
A documented agreement about a dataset's schema, semantics, quality and ownership.
Data engineer
A practitioner who builds reliable systems for collecting, transforming and serving data.
Data frame
A labelled two-dimensional structure widely used for analysis in Python and related tools.
Data freshness
The degree to which available data reflects the latest required source updates.
Data governance
Roles, policies and controls for data quality, security, access, retention and accountability.
Data lake
A scalable repository that stores raw and processed data in multiple formats.
Data lakehouse
An architecture combining flexible data-lake storage with warehouse-style management and analytics.
Data lineage
A record of where data originated, how it changed and where it is used.
Data mart
A curated subset of organisational data designed for a particular function or audience.
Data mesh
A decentralised data architecture that treats domains as accountable owners of interoperable data products.
Data model
A representation of entities, attributes, relationships and rules within a data system.
Data observability
Monitoring that reveals the freshness, volume, quality and lineage of data systems.
Data owner
The accountable person or function responsible for a data asset's meaning and governance.
Data pipeline
A repeatable flow that collects, validates, transforms and delivers data between systems.
Data product
A reusable, owned data asset designed to serve a defined set of users and decisions.
Data profiling
The systematic examination of distributions, missingness, uniqueness and anomalies before analysis.
Data quality
The degree to which data is accurate, complete, timely, consistent and fit for use.
Data retention
Rules determining how long information is stored and when it is archived or deleted.
Data science
An interdisciplinary practice combining programming, statistics, domain understanding and modelling to learn from data.
Data source
The system, file, service or process from which data originates.
Data transformation
A reproducible operation that reshapes, cleans, combines or enriches data.
Data validation
Checks confirming that data meets expected formats, ranges, relationships and business rules.
Data visualisation
The deliberate use of charts and visual structure to communicate comparisons, patterns and uncertainty.
Data warehouse
A governed repository optimised for integrated historical analysis and reporting.
Database
An organised system for storing, retrieving and managing data with defined structures and controls.
Database normalisation
The organisation of relational tables to reduce redundancy and update anomalies.
Dataset
A collection of related observations or records used for analysis, training or evaluation.
Decision tree
A branching model that predicts an outcome through a sequence of feature-based rules.
Deduplication
The identification and controlled removal or consolidation of duplicate records.
Descriptive analytics
Analysis that summarises what happened through metrics, comparisons and patterns.
Dimension
A descriptive field used to group, filter or explain a measure.
Dimension table
A warehouse table containing descriptive attributes used to group or filter facts.
Distributed database
A database whose data or processing is coordinated across multiple machines or locations.
Document database
A database that stores records as flexible documents rather than fixed relational rows.
ELT
Extract, Load, Transform: loading source data before transforming it within the target platform.
ETL
Extract, Transform, Load: a data workflow that collects source data, reshapes it and writes it to a target system.
Event stream
A continuous ordered flow of records describing actions or state changes.
Exploratory data analysis (EDA)
Early investigation using summaries and visualisation to understand structure, quality and patterns.
Fact table
A warehouse table containing measurable events linked to descriptive dimensions.
Feature engineering
The creation or transformation of model inputs using domain and data understanding.
Foreign key
A field that references a key in another table to represent a relationship.
Full outer join
A join returning matched rows plus unmatched rows from both inputs.
Granularity
The level of detail represented by one row, event or measurement.
GROUP BY
A SQL operation that forms groups before calculating aggregate results.
Hypothesis test
A statistical procedure for evaluating evidence against a stated assumption.
Imputation
The estimation or substitution of values where observations are missing.
Incremental load
A pipeline update that processes only records added or changed since the previous run.
Index
A database structure that accelerates selected lookups while adding storage and write cost.
Inner join
A join returning only rows whose join condition matches in both inputs.
Join
A relational operation that combines rows from tables using matching keys or conditions.
JSON
A text format representing nested data through objects, arrays and primitive values.
Key performance indicator (KPI)
A deliberately chosen metric used to monitor progress towards an important objective.
Left join
A join retaining every left-side row and matching right-side values where available.
Materialised view
A stored query result refreshed to improve repeated analytical access.
Mean
The arithmetic average calculated by dividing a sum by the number of observations.
Median
The middle value of an ordered dataset, useful when extreme values distort the mean.
Metadata
Information describing a dataset's structure, meaning, origin, ownership or operational characteristics.
Metric
A defined quantitative measure used to monitor behaviour, performance or outcomes.
Missing value
An observation whose expected field is absent, unknown or not recorded.
NoSQL
A family of non-relational database approaches designed for varied structures or scaling patterns.
NULL
A database marker indicating an absent or unknown value, distinct from zero or empty text.
Online analytical processing (OLAP)
Systems and operations optimised for multidimensional analysis of large datasets.
Online transaction processing (OLTP)
Systems optimised for frequent, reliable operational reads and writes.
Operational analytics
The use of timely data within recurring frontline workflows and decisions.
Outlier
An observation unusually distant from the broader pattern and worthy of investigation.
Parquet
A compressed columnar file format designed for efficient analytical storage and processing.
Partition
A logical division of data used to improve storage management and query performance.
Percentile
A value below which a stated percentage of ordered observations falls.
Primary key
A field or field combination that uniquely identifies a table row.
Probability distribution
A description of possible values and their associated likelihoods.
Query
A structured request to retrieve, combine, summarise or modify data in a database.
Query optimisation
The process of reducing the resources or time required to execute a database query.
Regression analysis
Statistical methods for estimating relationships between variables and a numerical outcome.
Relational database
A database organising data into connected tables governed by keys and constraints.
Right join
A join retaining every right-side row and matching left-side values where available.
Sample
A subset of a population selected for analysis or estimation.
Schema
The defined structure, fields, relationships and constraints of stored data.
Slowly changing dimension
A warehouse technique for preserving or updating historical descriptive attributes.
SQL
Structured Query Language, used to define, retrieve, combine and manage relational data.
Standard deviation
A measure of how widely observations vary around their mean.
Star schema
A warehouse model with a central fact table connected to dimension tables.
Statistical significance
A measure of how incompatible observed evidence is with a specified null hypothesis.
Streaming data
Data processed continuously or in near-real time as events arrive.
Structured data
Data organised into consistent fields and records with a defined schema.
Surrogate key
A generated identifier used instead of a natural business key.
Table
A relational structure that organises records into rows and named columns.
Time series
Observations recorded in chronological order for trend, seasonality or forecasting analysis.
Transaction
A logical unit of database work that succeeds or fails as a controlled whole.
Unstructured data
Information such as text, images or audio without a fixed tabular schema.
Variance
The average squared distance of observations from their mean.
Window function
A SQL calculation across related rows that preserves individual row output.
Questions about data and analytics vocabulary.
Which data terms matter most for analysts?+
Start with metric, dimension, granularity, aggregation, join, data quality, dashboard and statistical significance.
Do I need statistics before learning SQL?+
No. SQL can be learned through tables, filtering, grouping and joins. Statistics becomes increasingly valuable when you interpret variation, experiments and predictions.
What is the difference between a data lake and a data warehouse?+
A lake stores varied raw and processed data flexibly. A warehouse provides governed, integrated structures optimised for consistent analytics.
FROM DEFINITION TO PRACTICE
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