PG SQL ๐Ÿ“Œ SELECT ๐Ÿ“Œ MIN MAX

imsยท2021๋…„ 2์›” 22์ผ
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SQL

๋ชฉ๋ก ๋ณด๊ธฐ
8/12

๐Ÿ“Œ SELECT

๐ŸŽฏ <> , NOT IN

ํฌํ•จํ•˜์ง€ ์•Š๋Š” ๊ฒƒ

SELECT ANIMAL_ID,NAME FROM ANIMAL_INS WHERE INTAKE_CONDITION Not in ('Aged')

๋‹ค๋ฅธ ๋ฐฉ๋ฒ•์œผ๋กœ๋Š”

SELECT ANIMAL_ID,NAME FROM ANIMAL_INS WHERE INTAKE_CONDITION <> 'Aged'

์ด๋ ‡๊ฒŒ๋‚˜

SELECT ANIMAL_ID,NAME FROM ANIMAL_INS WHERE INTAKE_CONDITION != 'Aged'

์ด๋ ‡๊ฒŒ๋„ ํ•  ์ˆ˜ ์žˆ๋‹ค.

  • != ๋Œ€์‹ ์— <>๋ฅผ ์“ฐ๋Š”๊ฒŒ ํผํฌ๋จผ์Šค๊ฐ€ ์ข‹๋‹ค๊ณ  ํ•œ๋‹ค.

๐ŸŽฏ ์—ฌ๋Ÿฌ ๊ธฐ์ค€ ์ •๋ ฌํ•˜๊ธฐ

SELECT animal_id,name,datetime FROM animal_ins ORDER BY name ASC, datetime DESC
  • 1์ฐจ ๊ธฐ์ค€ + 2์ฐจ ๊ธฐ์ค€์œผ๋กœ ์ •๋ ฌํ•˜๊ณ  ์‹ถ์œผ๋ฉด, ORDER BY ๋‹ค์Œ์— ์ญ‰ ์ด์–ด์„œ ์จ์ฃผ๋ฉด ๋œ๋‹ค.

๐ŸŽฏ LIMIT

limit ์ด์šฉ

  • limit 2,4 ํ•˜๋ฉด 2~4๋ฒˆ์งธ ๊ฐ€์ ธ์˜จ๋‹ค.
SELECT name FROM ANIMAL_INS ORDER BY datetime limit 1

๐Ÿ“Œ SUM , MAX , MIN

๐ŸŽฏ MAX

๊ฐ€์žฅ ์ตœ๊ทผ์˜ ์‹œ๊ฐ„์„ ๊ฐ€์ ธ์™€๋ผ

SELECT max(datetime) FROM ANIMAL_INS 

๐ŸŽฏ COUNT

๋™๋ฌผ์˜ ์ˆซ์ž ์„ธ๋ผ

SELECT count(*) FROM ANIMAL_INS

๐ŸŽฏ distinct , is not

์ค‘๋ณต๋œ ์ด๋ฆ„ ์ œ๊ฑฐํ•˜๊ณ , null์ด ์•„๋‹Œ ๋™๋ฌผ ์ด๋ฆ„์˜ ๊ฐฏ์ˆ˜?

๐Ÿงฟ distinct = ์ค‘๋ณต์ œ๊ฑฐ

SELECT COUNT(DISTINCT name) FROM ANIMAL_INS WHERE name is not null
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