I take it you mean
trim(‘ab’ from ‘abcba')
(Double-quotes delimit identifiers, not character literals.)
SQL standard says:
6.30.11 If <trim function> is specified, then:
(a) Let S be the value of the <trim source>.
(b) If <trim character> is specified, then let SC be the
value of <trim character>; otherwise, let SC be <space>.
(c) If at least one of S and SC is the null value, then the result of
the <trim function> is the null value. If the length in characters of
SC is not 1 (one), then an exception condition is raised:
data exception — trim error.
<trim function> ::=
TRIM <left paren> <trim operands> <right paren>
<trim operands> ::=
[ [ <trim specification> ] [ <trim character> ] FROM ] <trim source>
<trim source> ::=
<character value expression>
<trim specification> ::=
LEADING
| TRAILING
| BOTH
In your example, Calclte should give an error because ‘ab’ does not have length
1.
You’ll see a comment to that effect in SqlOperatorBaseTest.testTrimFunc (but
sadly that part of the test is disabled).
Julian
> On Dec 7, 2017, at 1:59 AM, 于仲(重籽) <[email protected]> wrote:
>
> It seems that trim("ab" from "abcba")should return "c", according to
> https://calcite.apache.org/docs/reference.html
> However calcite removes only "a" of "ab", and this trim() returs "bcb". See
> implementation of SqlFunctions.trim()
> Is it a bug or something? :)
>
> Zhong Yu
