Enough to be useful.
SELECT
Reads data.
SELECT * FROM table_name LIMIT 10;
The asterisk means every column. LIMIT restricts how many rows come back, which is wise on a large table.
WHERE
Narrows which rows.
SELECT * FROM wp_options WHERE option_name = 'siteurl';
Without WHERE, you get everything.
UPDATE
Changes rows.
UPDATE wp_options SET option_value = 'https://example.com' WHERE option_name = 'siteurl';
The WHERE clause is what restricts it to one row. Without it, every row changes.
DELETE
Removes rows. Same warning about WHERE.
ORDER BY AND COUNT
ORDER BY sorts. COUNT(*) tells you how many rows match, which is useful before a change.
SELECT COUNT(*) FROM table WHERE condition;
Run that before any UPDATE or DELETE with the same condition. The number tells you what you are about to affect.
THE HABIT
SELECT first, always.
