What is the difference between INTEGER PRIMARY KEY and a regular PRIMARY KEY in SQLite?

Declaring a column as exactly INTEGER PRIMARY KEY makes it a direct alias for the table's internal rowid, meaning lookups by that column hit the B-tree's key directly — the fastest possible access path. A PRIMARY KEY on a non-integer column (or declared with WITHOUT ROWID), or a composite primary key across multiple columns, doesn't get this same rowid-aliasing behavior.

CREATE TABLE fast_lookup (
    id INTEGER PRIMARY KEY,   -- aliases rowid: fastest lookups
    name TEXT
);

CREATE TABLE composite_key (
    a TEXT,
    b TEXT,
    PRIMARY KEY (a, b)        -- composite key; no rowid alias
);

This distinction matters for performance-sensitive schema design: if a table's natural primary key is a single integer, declaring it as INTEGER PRIMARY KEY gets you the fastest lookup path essentially for free, whereas any other kind of primary key requires a normal (still efficient, but comparatively slower) B-tree index traversal.

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