SQL - MySQL, ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค ์ •๊ทœํ™”, Foreign Key, JOIN
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๐Ÿงฉ SQL
โœ… ๋ฐ์ดํ„ฐ๋ฒ ์ด์Šค ์ •๊ทœํ™”๋ž€? (Normalization)๋ฐ์ดํ„ฐ ์ค‘๋ณต์„ ์ค„์ด๊ณ , ๊ตฌ์กฐ๋ฅผ ๊น”๋”ํ•˜๊ฒŒ ๋งŒ๋“ค์–ด ๋ฌด๊ฒฐ์„ฑ์„ ์œ ์ง€ํ•˜๋Š” ์„ค๊ณ„ ๋ฐฉ๋ฒ• โ‘  ์ œ1์ •๊ทœํ˜• (1NF)์ปฌ๋Ÿผ์€ ์›์ž๊ฐ’(Atomic)๋งŒ ๊ฐ€์ ธ์•ผ ํ•œ๋‹ค โ‘ก ์ œ2์ •๊ทœํ˜• (2NF)๋ถ€๋ถ„ ํ•จ์ˆ˜ ์ข…์† ์ œ๊ฑฐ โ‘ข ์ œ3์ •๊ทœํ˜• (3NF)์ดํ–‰์  ์ข…์† ์ œ๊ฑฐ โœ… Foreign Key๋‹ค๋ฅธ ํ…Œ์ด๋ธ”์˜ Primary Key๋ฅผ ์ฐธ์กฐํ•˜๋Š” Column CREATE TABLE dogs ( dog_id BIGINT UNSIGNED PRIMARY KEY AUTO_INCREMENT, name VARCHAR(50) NOT NULL, weight DECIMAL(5, 2), date_of_birth DATE, owner_id BIGINT UNSIGNED, breed_id B..