Major Description
Currently, casting decimal as string type will result in Strings with exponential notations if the adjusted exponent is less than -6. This is consistent with BigDecimal.toString https://docs.oracle.com/javase/8/docs/api/java/math/BigDecimal.html#toString
This is different from external databases like PostgreSQL/Oracle/MS SQL server. It doesn't compliant with the ANSI SQL standard either.
I suggest always using the plain string in the casting.
After discussions, I decide to put the new behavior on ANSI SQL mode.
