SQL Glossary

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A
Aggregation
Combining multiple rows into one via functions like COUNT, SUM, AVG, MIN, MAX.
Authorization
GRANT/REVOKE control over who can read or modify data.
C
CTE (Common Table Expression)
Named temporary result via WITH clause; enables recursion with WITH RECURSIVE.
Constraint
Rule on data: PRIMARY KEY, FOREIGN KEY, UNIQUE, CHECK, NOT NULL.
D
DDL / DML
DDL (CREATE/ALTER/DROP) defines schema; DML (SELECT/INSERT/UPDATE/DELETE) manipulates data.
J
Join
Combining rows from two relations via a predicate (INNER, LEFT/RIGHT/FULL OUTER, NATURAL, USING).
N
NULL / Three-Valued Logic
NULL is unknown; comparisons yield UNKNOWN (TRUE/FALSE/UNKNOWN). WHERE keeps only TRUE.
Normalization
Decomposing schemas to reduce redundancy (1NF, 2NF, 3NF, BCNF).
W
Window Function
Function over a window of rows via OVER (PARTITION BY ... ORDER BY ...), e.g., RANK, ROW_NUMBER, LAG.