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SQL Glossary Terms

SQL Seeker's SQL Terminology Glossary is your quick reference for understanding essential SQL concepts.

New to SQL or need a refresher on key terms? From foundational terms like primary key to advanced topics like index and subquery, this guide provides clear definitions and examples to boost your SQL knowledge.

SQL Terminology Reference Table

Term

Category

Definition

Example

Primary Key

Constraints

Unique identifier for a table's rows.

CREATE TABLE users (id INT PRIMARY KEY, name VARCHAR(50));

Foreign Key

Constraints

Column linking to another table's primary key.

CREATE TABLE orders (id INT, user_id INT, FOREIGN KEY (user_id) REFERENCES users(id));

Index

Indexes

Structure to speed up query performance.

CREATE INDEX idx_name ON users(name);

Unique Constraint

Constraints

Ensures column values are unique.

CREATE TABLE users (email VARCHAR(50) UNIQUE);

Table

Schema

Structure storing data in rows and columns.

CREATE TABLE products (id INT, name VARCHAR(50));

Column

Schema

Field storing a specific data type in a table.

ALTER TABLE users ADD COLUMN email VARCHAR(50);

Row

Schema

Single record in a table.

INSERT INTO users (name, age) VALUES ('Alice', 30);

Join

Joins

Combines data from multiple tables.

SELECT users.name, orders.amount FROM users INNER JOIN orders ON users.id = orders.user_id;

Subquery

Queries

Nested query within another query.

SELECT name FROM users WHERE id IN (SELECT user_id FROM orders);

Aggregate

Aggregates

Function summarizing data, e.g., COUNT, SUM.

SELECT COUNT(*) FROM orders;

Schema

Schema

Database structure defining tables and relationships.

CREATE SCHEMA sales;

View

Schema

Virtual table based on a query.

CREATE VIEW active_users AS SELECT * FROM users WHERE active = true;

Trigger

Automation

Procedure executed on table events.

CREATE TRIGGER update_timestamp AFTER UPDATE ON users FOR EACH ROW UPDATE users SET updated_at = NOW();

Transaction

Transactions

Set of operations executed as a unit.

BEGIN; INSERT INTO orders (amount) VALUES (100); COMMIT;

Alias

Queries

Temporary name for a column or table.

SELECT name AS full_name FROM users;

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