First let's take a look at translate function definition:
TRANSLATE(expr, from_string, to_string): TRANSLATE returns expr with all
occurrences of each character in from_string replaced by its corresponding
character in to_string. Characters in expr that are not in from_string are not replaced.
If expr is a character string, then you must enclose it in single quotation marks.
The argument from_string can contain more characters than to_string. In this case,
the extra characters at the end of from_string have no corresponding characters
in to_string. If these extra characters appear in char, then they are removed
from the return value.
i.e. TRANSLATE(some_string,'123','abc'): 1 will be replaced by a, 2 by b, 3 by c(I will use arrow -> instead of "replaced by" further)
Now let's take a look at our examples:
TRANSLATE('1','123',' '): 1 -> " ", 2->nothing, 3->nothing.
(nothing means removed from the return value, see definition)
Result of above function is string consisted of whitespace - " "