concat과 time을 사용하여 date 쉽게 변환하기

   concat과 time을 사용하여 날짜변경 (년,월,일 ... ) 쉽게 변환하기

   concat

CONCAT(str1,str2,...)

Returns the string that results from concatenating the arguments. May have one or more arguments. If all arguments are nonbinary strings, the result is a nonbinary string. If the arguments include any binary strings, the result is a binary string. A numeric argument is converted to its equivalent nonbinary string form.

CONCAT() returns NULL if any argument is NULL.

mysql> SELECT CONCAT('My', 'S', 'QL');
        -> 'MySQL'
mysql> SELECT CONCAT('My', NULL, 'QL');
        -> NULL
mysql> SELECT CONCAT(14.3);
        -> '14.3'

For quoted strings, concatenation can be performed by placing the strings next to each other:

mysql> SELECT 'My' 'S' 'QL';
        -> 'MySQL'

https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_concat

   time

TIME(expr)

Extracts the time part of the time or datetime expression expr and returns it as a string.

This function is unsafe for statement-based replication. A warning is logged if you use this function when binlog_format is set to STATEMENT.

mysql> SELECT TIME('2003-12-31 01:02:03');
        -> '01:02:03'
mysql> SELECT TIME('2003-12-31 01:02:03.000123');
        -> '01:02:03.000123'

   SQL Query

update MY_TABLE set datetime = concat('2018-08-12 ', time(datetime))