怎么用正则表达式替换函数将SQL中的decode用case when代替

用case when通用性和可读性更好

比如：
select decode(3-1,2,'right','wrong') from dual;

替换成

select case when 3-1 =2 then
'right'
else
'wrong'
end case
from dual;

select code from test

code
------
select decode(3-1,2,'right','wrong') from dual

select regexp_replace(code,'decode\(([^,]+),([^,]+),([^,]+),([^,]+)\)(.*)','case when \1 = \2 then \3 else \4 end case \5') new_code
from test

new_code
------
select case when 3-1 = 2 then 'right' else 'wrong' end case from dual

出一个有挑战性的问题---用pl/sql解析SQL

先出一个初步的需求，对于insert/update 语句。怎么取得source table 和 target table

example 1

insert into table_a
select *  from table_b

这里，  table_a 是target_table,  table_b 是source table

example 2

update table_c
set id=(select id from table_d)

这里，  table_d 是target_table,  table_c 是source table

select regexp_replace('insert into table_c set id=(select id from table_d)','(^.*)((update)|(into))(\s+)(\S+)(\s+.*)','\6') source_table,
regexp_replace('insert into table_c set id=(select id from table_d)','(^.+)(from)(\s+)(\S+)([\)| ]+.*)','\4') target_table
from dual