Functional dependency X → Y means each X value corresponds to exactly one Y value. Determinant set X and dependent set Y are commonly used terms. Trivial dependency occurs when Y is a subset of X
SQL joins combine data from multiple tables into result sets. Tables are arranged horizontally in the FROM clause. Leftmost table is the base table, rightmost table is the joined table
CHAR stores fixed-length strings from 0 to 255 characters. Values are right-padded with spaces to specified length. Trailing spaces are removed unless PAD_CHAR_TO_FULL_LENGTH mode is enabled
Check constraints enforce Boolean conditions on column values. Constraints can be named and referenced across multiple columns. Constraints must refer only to new or updated rows. PostgreSQL assumes constraint conditions are immutable
Foreign key references primary key of another table. Creates parent-child relationship for data integrity. Ensures all related records exist in related tables
SQL joins bring together data from multiple tables in a single query. Tables contain rows of similar or related data. Joins are performed using the JOIN keyword