Oracle＜--＞MySQL

to_char(‘123.456’, FM9,990.09)
format(123.456, 2) — default:en_US(9,999,999)

to_char(‘123’)
cast(‘123’ as unsigned int) — unsigned/signed int, decimal(10,2)

to_date(‘19980210’, ‘yyyy-mm-dd’)
date_format(‘19980210’, ‘%Y-%m-%d’)

decode(1,null,3,4,5,6)
case 1 when 1 is null then 3 when 4 then 5 else 6

a || b
concat(a,b)