リレーショナルデータベースの基本まとめ（スライド資料と動画とプログラム例）

CREATE TABLE tosyo (
    book TEXT,
    who TEXT,
    what TEXT,
    at DATETIME);
INSERT INTO tosyo VALUES('赤', 'XX', '貸出', NOW());
INSERT INTO tosyo VALUES('赤', 'XX', '返却', NOW());
INSERT INTO tosyo VALUES('青', 'YY', '貸出', NOW());
INSERT INTO tosyo VALUES('緑', 'ZZ', '貸出', NOW());
SELECT * FROM tosyo;
SELECT  who, COUNT(*) FROM tosyo GROUP BY who;
SELECT COUNT(*) FROM tosyo WHERE what='貸出';