--------自定义函数f_change_days---------------------------------------------------------------- CREATE OR REPLACE FUNCTION f_change_days(i_day bigint, i_number bigint) RETURNS bigint LANGUAGE plpgsql AS $$ DECLARE BEGIN return (to_char(to_date(i_day::varchar,'yyyymmdd')+i_number,'yyyymmdd'))::numeric; end; $$; / ------------------------------------------------------------------------------------------------------------- 当调用 时报错： select F_CHANGE_DAYS(20110101,-1); 报错信息： [2022-10-09 16:50:54.164 CST] : [ERROR] 执行失败 错误代码：[0][SQLErrorCode : 9683][192.168.4.14:50311/192.168.2.23:15400] ERROR: operator does not exist: timestamp without time zone + bigint 建议:No operator matches the given name and argument type(s). You might need to add explicit type casts. 在位置:referenced column: to_char PL/pgSQL function f_change_days(bigint,bigint) line 4 at RETURN referenced column: f_change_daysLine Number: 1 当把函数拓传入参数及返回参数的数据类型都改为INTEGER时，就不会报错，如下： --------修改后自定义函数f_change_days---------------------------------------------------------------- CREATE OR REPLACE FUNCTION f_change_days(i_day integer, i_number integer) RETURNS integer LANGUAGE plpgsql AS $$ DECLARE BEGIN return (to_char(to_date(i_day::varchar,'yyyymmdd')+i_number,'yyyymmdd'))::numeric; end; $$; / ------------------------------------------------------------------------------------------------------------- 调用时正常： select F_CHANGE_DAYS(20110101,-1); 正常输出： 20101231 我想问的时，函数的数据类型必须强一致，不太明白其中原理