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Converting text to numbers | ||
A table is created ...
create table safe_to_number_t ( txt varchar2(10) );
... and filled with text of which some can be converted to numbers:
insert into safe_to_number_t values ('1.0' ); insert into safe_to_number_t values ('1' ); insert into safe_to_number_t values ('22.9' ); insert into safe_to_number_t values ('FOO' ); insert into safe_to_number_t values ('-8.99' ); insert into safe_to_number_t values ('-.22' ); insert into safe_to_number_t values ('-BAR' ); insert into safe_to_number_t values ('23-45' );
However, some txts cannot be converted...
... and an error is thrown:
ERROR: ORA-01722: invalid number
So, a function is created that can safely convert strings to numbers. When the string is inconvertable, it returns null:
create function safe_to_number(txt in varchar2) return number is begin return to_number(txt); exception when value_error then return null; end safe_to_number; / select safe_to_number(txt), txt from safe_to_number_t; SAFE_TO_NUMBER(TXT) TXT ------------------- ---------- 1 1.0 1 1 22.9 22.9 FOO -8.99 -8.99 -.22 -.22 -BAR 23-45 select safe_to_number(txt), txt from safe_to_number_t; With regexp_substr
In 10g, it's possible to use regexp_substr for the same effect:
select to_number( regexp_substr(txt,'^[-]?[[:digit:]]*\.?[[:digit:]]*$') ) the_number, txt from safe_to_number_t; |