제약 조건으로 데이터 품질 향상

SQL로 배우는 관계형 데이터베이스 입문

Timo Grossenbacher

Data Journalist

무결성 제약 조건

CREATE TABLE weather (
 temperature integer,
 wind_speed text);

SELECT temperature * wind_speed AS wind_chill
FROM weather;

operator does not exist: integer * text
HINT: No operator matches the given name and argument type(s). 
You might need to add explicit type casts.

SELECT temperature * CAST(wind_speed AS integer) AS wind_chill
FROM weather;

SQL로 배우는 관계형 데이터베이스 입문