timestamp（）是否不接受函数参数作为输入？

Question

I am using sql in postgresql

cast(col as timestamp($1))

It gives me error around parameter

The sql works when I give the number directly:

cast(col as timestamp(1))

So timestamp do not take function parameter?

Answer 1

The precision modifier of the timestamp type is part of the type name and cannot be parameterized in plain SQL. That's not a function, even though the syntax with parentheses looks the same.

You would need dynamic SQL for that. In a PL/pgSQL function build the statement as string and run it with EXECUTE . Something like:

EXECUTE 'SELECT col::timestamp(' || $1 || ')'
INTO my_var;

$1 being type integer . Not a string type like text , or you have a possible SQL injection hole.