Di seguito sono riportate tre implementazioni separate per ciascuno di SQL Server, MySQL e Oracle. Nessuno usa (o può) lo stesso approccio, quindi non sembra esserci un modo DBMS incrociato per farlo. Per MySQL e Oracle, viene mostrato solo il semplice test intero; per SQL Server viene visualizzato il test numerico completo.
Per SQL Server:nota che isnumeric('.') restituisce 1.. ma non può essere effettivamente convertito in float. Alcuni testi come '1e6' non possono essere convertiti direttamente in numerici, ma puoi passare tramite float, quindi numerico.
;with tmp(x) as (
select 'db01' union all select '1' union all select '1e2' union all
select '1234' union all select '' union all select null union all
select '1.2e4' union all select '1.e10' union all select '0' union all
select '1.2e+4' union all select '1.e-10' union all select '1e--5' union all
select '.' union all select '.123' union all select '1.1.23' union all
select '-.123' union all select '-1.123' union all select '--1' union all
select '---1.1' union all select '+1.123' union all select '++3' union all
select '-+1.123' union all select '1 1' union all select '1e1.3' union all
select '1.234' union all select 'e4' union all select '+.123' union all
select '1-' union all select '-3e-4' union all select '+3e-4' union all
select '+3e+4' union all select '-3.2e+4' union all select '1e1e1' union all
select '-1e-1-1')
select x, isnumeric(x),
case when x not like '%[^0-9]%' and x >'' then convert(int, x) end as SimpleInt,
case
when x is null or x = '' then null -- blanks
when x like '%[^0-9e.+-]%' then null -- non valid char found
when x like 'e%' or x like '%e%[e.]%' then null -- e cannot be first, and cannot be followed by e/.
when x like '%e%_%[+-]%' then null -- nothing must come between e and +/-
when x='.' or x like '%.%.%' then null -- no more than one decimal, and not the decimal alone
when x like '%[^e][+-]%' then null -- no more than one of either +/-, and it must be at the start
when x like '%[+-]%[+-]%' and not x like '%[+-]%e[+-]%' then null
else convert(float,x)
end
from tmp order by 2, 3
Per MySQL
create table tmp(x varchar(100));
insert into tmp
select 'db01' union all select '1' union all select '1e2' union all
select '1234' union all select '' union all select null union all
select '1.2e4' union all select '1.e10' union all select '0' union all
select '1.2e+4' union all select '1.e-10' union all select '1e--5' union all
select '.' union all select '.123' union all select '1.1.23' union all
select '-.123' union all select '-1.123' union all select '--1' union all
select '---1.1' union all select '+1.123' union all select '++3' union all
select '-+1.123' union all select '1 1' union all select '1e1.3' union all
select '1.234' union all select 'e4' union all select '+.123' union all
select '1-' union all select '-3e-4' union all select '+3e-4' union all
select '+3e+4' union all select '-3.2e+4' union all select '1e1e1' union all
select '-1e-1-1';
select x,
case when x not regexp('[^0-9]') then x*1 end as SimpleInt
from tmp order by 2
Per Oracle
case when REGEXP_LIKE(col, '[^0-9]') then col*1 end
