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목록2023/09/16 (1)
HJW's IT Blog
DB: Chapter 7(Complex Queries)
#Comparisons Involving NULL & Three-Valued Logic > NULL : unknown value, not applicable attribute > Three-valued Logic > IS [NOT] NULL ex) Retrieve the names of all employees who do not have supervisors SELECT Fname, Lname FROM EMPLOYEE WHERE Super_ssn IS NULL > IN 연산 > 중첩 질의 (Nested Query) > PROJECT 테이블에서 Dnum 이 5 인요소들의 Pnumber 를 골라 해당하는 Pname 을 출력 SELECT Pname FROM PROJECT WHERE Plocation='Hus..
Database
2023. 9. 16. 14:10