SQL: Structured Query Language, used to work with databases
Database: An organized collection of data
Table: Rows and columns of data in a database
Row (record): One entry in a table
Column (field): One attribute shared by all rows
Primary key: A column that uniquely identifies each row
Foreign key: A column linking to the primary key of another table
SELECT: Gets data from a table
SELECT *: Gets every column
FROM: Names the table to read
WHERE: Filters rows by a condition
AND, OR, NOT: Combine or negate conditions
ORDER BY: Sorts the results
ASC / DESC: Sort ascending or descending
LIMIT: Restricts how many rows are returned
DISTINCT: Removes duplicate values from results
LIKE: Matches text patterns
% wildcard: Matches any number of characters in LIKE
_ wildcard: Matches exactly one character in LIKE
IN: Matches any value in a list
BETWEEN: Matches a range of values
IS NULL: Tests for missing values
AS (alias): Gives a column or table a temporary name
INSERT INTO: Adds new rows to a table
VALUES: Gives the values for an insert
UPDATE: Changes data in existing rows
SET: Names the columns to change in an update
DELETE FROM: Removes rows
CREATE TABLE: Makes a new table
ALTER TABLE: Changes a table's structure
DROP TABLE: Deletes a table entirely
CREATE INDEX: Makes a table lookup faster
COUNT(): Counts rows
SUM(): Adds up values
AVG(): Finds the average
MIN(): Finds the smallest value
MAX(): Finds the largest value
GROUP BY: Groups rows to use with aggregate functions
HAVING: Filters groups after grouping
JOIN: Combines rows from two tables
INNER JOIN: Keeps only rows that match in both tables
LEFT JOIN: Keeps all rows from the left table and matches from the right
RIGHT JOIN: Keeps all rows from the right table and matches from the left
FULL OUTER JOIN: Keeps all rows from both tables
CROSS JOIN: Pairs every row of one table with every row of another
UNION: Combines results of two queries, removing duplicates
UNION ALL: Combines results and keeps duplicates
Subquery: A query inside another query
EXISTS: Tests whether a subquery returns rows
CASE WHEN: Conditional logic inside a query
NULL: A missing or unknown value
NOT NULL: A column must always have a value
UNIQUE: All values in a column must be different
DEFAULT: A value used when none is given
CHECK: A rule that values must satisfy
Transaction: A group of operations that succeed or fail together
COMMIT: Saves a transaction
ROLLBACK: Undoes a transaction
View: A saved query that acts like a table
Index: A structure that speeds up searches
Normalization: Organizing tables to reduce repeated data
Schema: The structure of a database
Relational database: A database storing data in related tables
One-to-many relationship: One row in a table relates to many rows in another
Many-to-many relationship: Many rows relate to many, using a join table
ACID: Atomicity, Consistency, Isolation, Durability, properties of reliable transactions
SQL injection: An attack that sneaks harmful SQL into input; prevent with parameterized queries
Parameterized query: A query with placeholders for safe user input
MySQL, PostgreSQL, SQLite: Popular SQL database systems
NoSQL: Databases that don't use traditional tables, like document stores
Query: A request for data
CRUD: Create, Read, Update, Delete

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