Ron <ronljohnsonjr(at)gmail(dot)com> writes:
> On 7/6/23 04:19, gzh wrote:
>> when I execute the sql below , the to_char function caused the following
>> error.
>> select TO_CHAR('1000000');
> Isn't '1000000' already a character string?
Nope; in the mind of the Postgres parser, it's a literal of unknown type,
with the actual type to be inferred from context. There is a small
preference for resolving such a thing as being of text type, but only a
small one. The rules are exactly the same as for an undecorated NULL
constant.
regards, tom lane