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[PostgreSQL / mySQL] COALESCE NULL ์ฒดํฌ ํ•จ์ˆ˜

COALESCE : param1์˜ ๊ฐ’์ด NULL์ผ ๊ฒฝ์šฐ param2์˜ ๊ฐ’์œผ๋กœ ๋ฐ˜ํ™˜ COALESCE(param1, param2) * COALESCE(ํ‘œํ˜„์‹....์—ฌ๋Ÿฌ๊ฐœ) : ์ฒซ๋ฒˆ์งธ ์ธ์ž์˜ ๊ฐ’์ด NULL ์ด๋ฉด ๋‘๋ฒˆ์งธ ์ธ์ž๊ฐ’์„ ๋ฆฌํ„ด, ๋ชจ๋“  ์ธ์ž๊ฐ€ NULL ์ด๋ฉด NULL์„ ๋ฆฌํ„ด * NVL ๋˜๋Š” ISNULL(ํ‘œํ˜„์‹1, ํ‘œํ˜„์‹2) : ํ‘œํ˜„์‹1 ์˜ ๊ฒฐ๊ฐ€๊ฐ’์ด NULL ์ด๋ฉด ํ‘œํ˜„์‹2์˜ ๊ฐ’์„ ์ถœ๋ ฅ * NULLIF(ํ‘œํ˜„์‹1, ํ‘œํ˜„์‹2) : ํ‘œํ˜„์‹1์ด ํ‘œํ˜„์‹2์™€ ๊ฐ™์œผ๋ฉด NULL ์„, ๊ฐ™์ง€ ์•Š์œผ๋ฉด ํ‘œํ˜„์‹1 ์„ ๋ฆฌํ„ด. - ํŠน์ • ๊ฐ’์„ NULL๋กœ ์น˜ํ™˜ํ•  ๋•Œ ์ฃผ๋กœ ์‚ฌ์šฉ.
DB 2022.02.14
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