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When joining two tables, you have to have a foreign key. Try to join two tables using foreign key which type is Int. In terms of performance, it makes huge difference compared to the case using String type as a foreign key. When Indexing, the speed with string type and int type are completely different. 테이블 두 개를 조인할 때, 외래키를 사용해야 한다. 외래키를 만들 때는, 되도록이면 string 타입보다는 int 타입을 사용하도록 해야 한다. 인덱싱을 할 때, i..

From Mysql Ver. 5, data can be stored as boolean type. The problem is when you check on mysql database, it is not stored as true or false, but stored as 1 or 0. In fact, it is not boolean type. It is TINYINT(1). Therefore, when you bring the data, you should use 1 or 0. OR IF( , 'true', 'false') as

SELECT ANIMAL_ID, NAME, DATE_FORMAT(DATETIME, '%Y-%m-%d')AS '날짜' FROM ANIMAL_INS ORDER BY ANIMAL_ID;

SELECT INS.ANIMAL_ID, INS.NAME FROM ANIMAL_INS as INS INNER JOIN ANIMAL_OUTS as OUTS ON INS.ANIMAL_ID = OUTS.ANIMAL_ID ORDER BY (OUTS.DATETIME - INS.DATETIME) DESC LIMIT 2;

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 ORDER BY ANIMAL_ID; *** CASE when으로 사용하는 경우!!!! 꼭 잘 외워두기

1. 첫 번째 방법 SELECT ANIMAL_ID, NAME, SEX_UPON_INTAKE FROM ANIMAL_INS WHERE NAME = 'Lucy' OR NAME = 'Ella' OR NAME = 'Pickle' OR NAME = 'Rogan' OR NAME = 'Sabrina' OR NAME = 'Mitty'; 2. 두 번째 방법 SELECT ANIMAL_ID, NAME, SEX_UPON_INTAKE FROM ANIMAL_INS WHERE NAME IN ( 'Lucy', 'Ella', 'Pickle', 'Rogan', 'Sabrina','Mitty');

SELECT INS.ANIMAL_ID, INS.ANIMAL_TYPE, INS.NAME FROM ANIMAL_INS as INS INNER JOIN ANIMAL_OUTS as OUTS ON INS.ANIMAL_ID = OUTS.ANIMAL_ID WHERE INS.SEX_UPON_INTAKE LIKE 'Intact%' AND (OUTS.SEX_UPON_OUTCOME LIKE 'Spayed%' OR OUTS.SEX_UPON_OUTCOME LIKE 'Neutered%' ) ORDER BY INS.ANIMAL_ID; 내가 한 방법은 위의 방식인데 다른 사람들이 한 걸 찾아보니, intake와 outcome이 다르다는 조건을 이용해서 구한 사람도 있었다. 하지만, 조건이 여러 개 더 주어지면 정확하게 하는 편이 나..

SELECT INS.NAME, INS.DATETIME FROM ANIMAL_INS as INS LEFT OUTER JOIN ANIMAL_OUTS as OUTS ON INS.ANIMAL_ID = OUTS.ANIMAL_ID WHERE OUTS.ANIMAL_ID is NULL ORDER BY INS.DATETIME LIMIT 3;