코테 대비

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Java

 

초기셋팅

throws Exception

 

우선순위 큐

PriorityQueue<Integer> q =new PriorityQueue<>();

 

배열 복사하기

for(int i=0; i<array.length; i++) {
			array_c[i]=array[i].clone();
		}

배열 && 리스트 정렬

// 배열
Arrays.sort(array,Collections.reverseOrder());

//리스트
Collections.sort(arraylist, Collections.reverseOrder());

 

2차 배열 정렬

//오름차순
Arrays.sort(array,(o1,o2)->{
   if(o1[0]==o2[0]) {
      return Integer.compare(o1[1], o2[1]);
   }else {
      return Integer.compare(o1[0], o2[0]);
   }
});

//내림차순
Arrays.sort(array,Collections.reverseOrder((o1,o2)->{
   if(o1[1]==o2[1]) {
        return Integer.compare(o1[0], o2[0]);
     }else {
        return Integer.compare(o1[1], o2[1]);
     }
}));

 

 

 

 

 

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My SQL

상위 n개

SELECT * FROM 테이블
LIMIT 1

날짜 차이

DATEDIFF(END_DATE,START_DATE)+1)

SELECT TIMESTAMPDIFF(SECOND, '2017-03-01', '2018-03-28');

중복 제거

SELECT COUNT (DISTINCT NAME) AS COUNT
FROM ANIMAL_INS
WHERE NAME IS NOT NULL

NULL 처리

IFNULL(NAME,"No name")

JOIN

JOIN ANIMAL_OUTS AS B
ON A.ANIMAL_ID = B.ANIMAL_ID

LEFT JOIN ANIMAL_OUTS AS B
ON A.ANIMAL_ID = B.ANIMAL_ID

CASE

SELECT ANIMAL_ID, NAME,
CASE WHEN SEX_UPON_INTAKE LIKE "%Neutered%" OR SEX_UPON_INTAKE LIKE "%Spayed%"
THEN "O"
ELSE "X"
END
AS "중성화"
FROM ANIMAL_INS

DATETIME -> DATE

DATE_FORMAT(DATETIME, '%Y-%m-%d')