CREATE DEFINER=`root`@`%` FUNCTION `decode_oracle`(pattern VARCHAR(255),string_a VARCHAR(255),string_b VARCHAR(255),string_c VARCHAR(255)) RETURNS varchar(255) CHARSET utf8mb4
BEGIN
DECLARE result VARCHAR(255) DEFAULT "";
#正常对比函数
if pattern=string_a then
set result = string_b;
ELSEIF pattern=string_b then
set result = string_c;
ELSEIF pattern=string_c then
set result = string_c;
#处理空值
ELSEIF string_a is null then
if pattern is not null then
set result = string_c;
ELSE