SQL Training #26 - 33 함수들 정보
SQL Training #26 - 33 함수들본문
SQL Round Function
select * from simpledb.employee;
select avg(salary) from simpledb.employee;
select round(avg(salary), 2) from simpledb.employee;
마이너스로도 사용이 가능합니다. 당연히 반올림되죠
select round(avg(salary), -2) from simpledb.employee;
https://www.youtube.com/watch?v=b0lOdcVI4CE&list=PLD20298E653A970F8&index=26
SQL Cast Function
Type이 BINARY
, CHAR
, DATE
, DATETIME
, TIME
,DECIMAL
, SIGNED
, UNSIGNED
만 지원되네요. ( http://www.mysqltutorial.org/mysql-cast/ )
select cast(salary as signed ) from simpledb.employee;
select cast(salary as char(50) ) from simpledb.employee;
+ 대신에 concat를 사용하기 때문에 자동으로 숫자는 String으로 변경.
select concat(employee_name, salary) from simpledb.employee;
https://www.youtube.com/watch?v=obKnx6IY5X4&list=PLD20298E653A970F8&index=27
SQL Convert Function
Mysql 에서는 Cast()와 Convert() 같은것 같습니다.
https://www.youtube.com/watch?v=fqwD7h3kkMw&list=PLD20298E653A970F8&index=28
SQL Concatenate
https://www.w3schools.com/sql/func_mysql_concat.asp
https://www.youtube.com/watch?v=CA9RFedFXlg&list=PLD20298E653A970F8&index=29
SQL Substring
https://www.w3schools.com/sql/func_mysql_substring.asp
시작은 1부터 0을 하면 첫글자 앞이네요
select substring(employee_name, 1, 3) from simpledb.employee;
https://www.youtube.com/watch?v=3U96oI37MgE&list=PLD20298E653A970F8&index=30
SQL CharIndex - Instring
MySQL에서는 locate를 사용합니다. https://www.w3schools.com/sql/func_mysql_locate.asp
select locate('R', employee_name) from simpledb.employee;
https://www.youtube.com/watch?v=lStyUa2vRHE&list=PLD20298E653A970F8&index=31
SQL Trim, Rtrim, Ltrim
https://www.w3schools.com/sql/func_mysql_trim.asp
https://www.w3schools.com/sql/func_mysql_rtrim.asp
https://www.w3schools.com/sql/func_mysql_ltrim.asp
select ' hello ';
select trim(' hello ');
https://www.youtube.com/watch?v=yzj3Jey-syM&list=PLD20298E653A970F8&index=32
SQL Length
https://www.w3schools.com/sql/func_mysql_length.asp
len대신에 LENGTH
https://www.youtube.com/watch?v=e-qPy7CAH4Y&list=PLD20298E653A970F8&index=33
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