[MYSQL/MARIA] 복합 UNIQUE KEY와 NULLABLE

DB(SQL)/mysql|maria

[MYSQL/MARIA] 복합 UNIQUE KEY와 NULLABLE

24시간초보 2021. 6. 2. 10:58

Composite Unique key constraint with multiple null value in one of the column

예를들어 room_id와 camera_number를 복합 unique key로 설정하였다.

그리고 room_id는 nullable 하다.

그럴 경우 아래와 같이 했을 때 error가 날까?

결론 아니다.

왜?

null 은 값이 아니라 비교가 불가능 하기 때문.

테이블 구성할때 이부분을 조심해야할것 같다.

https://stackoverflow.com/questions/54287281/composite-unique-key-constraint-with-multiple-null-value-in-one-of-the-column

Composite Unique key constraint with multiple null value in one of the column

I have a unique key on table x with 3 column (a,b,c) where a,b,c are foreign keys and c can be null in x table. a b c - - ---- 1 1 1 1 1 2 1 1 NULL 1 1 NUll Above rows are valid on MySQL and

stackoverflow.com

https://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:39951226964354

unique index with null values - Ask TOM

You Asked Hello Tom, I have this situation: With a table like create table test (id number not null, name varchar2(10) not null, source_id number); (actually the real tables have more columns, but for this question these are enough) and with this rows inse

asktom.oracle.com