#4 SQL 문자함수 잘 이용하기

 

SELECT country_name as 원본, lower(capital_city) as 소문자, upper(continent) as 대문자 FROM country;
SELECT country_name, length(country_name) as 길이 FROM country;
SELECT (country_name || '의 수도는 ' || capital_city || ' 입니다!') as 수도소개 FROM country;
SELECT continent as 원본, substr(continent, 1,3) FROM country;
SELECT continent as 원본, instr(continent, 'A') FROM country;
SELECT continent as 원본, lpad(continent, 10, 'A') FROM country;
SELECT capital_city as 원본, trim(capital_city), ltrim(capital_city), rtrim(capital_city) FROM country;
SELECT continent as 원본, replace(continent, 'A', '@') FROM country;

(1) 몇부터 몇까지만 끊고 싶을 때: substr(column, 시작할 위치, 끝날 위치)

(2) 특정문자를 찾고 싶을 때: instr(column, 찾고싶은문자)

(3) 특정문자로 채우고 싶을 때: lpad, rpad(column, 몇번째 까지, 채울문자)

(4) 공백 없애고 싶을 때: trim, ltrim, rtrim(column)

(5) 대체하고 싶을 때: replace(column, 이문자를, 요문자로)