SELECT, WHERE, ORDER BY, LIMIT
Try it: SELECT, WHERE, ORDER BY, LIMIT
How a SELECT query tests every row against the WHERE condition (keeping only rows where it is TRUE, not FALSE or NULL), then picks columns, removes duplicates with DISTINCT, sorts with ORDER BY and cuts with LIMIT.
How it works
- FROM: start with every row of the table.
- WHERE: evaluate the condition on each row. Comparisons with NULL give NULL (unknown); NOT, AND and OR follow three-valued logic, with AND binding tighter than OR. Only rows where the whole condition is TRUE are kept.
- SELECT picks the listed columns; DISTINCT then drops result rows that repeat an earlier one.
- ORDER BY sorts by each key in turn, ASC or DESC; SQLite puts NULL first when ascending and last when descending.
- LIMIT n keeps only the first n rows of the sorted result.
Default run (13 steps): SELECT title, plays FROM track WHERE plays >= 95 AND rating >= 4 ORDER BY plays DESC LIMIT 2. FROM: start with all 8 rows of track. … Result: 2 rows.
Simplified: A toy relational engine in the browser, not SQLite itself: a small structured query model built from the controls (no SQL text is parsed or executed), typed INTEGER/TEXT/NULL values, and tables of at most a few rows. Results were checked against Python's sqlite3 (SQLite 3.49). Ties in ORDER BY are broken by id here (by the selected columns with DISTINCT), and DISTINCT without ORDER BY keeps first-occurrence order; SQLite itself promises no order for ties. LIKE is case-insensitive for ASCII letters, as in SQLite.
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