Nedan finns tre separata implementeringar för var och en av SQL Server, MySQL och Oracle. Ingen använder (eller kan) samma tillvägagångssätt, så det verkar inte finnas ett korsvis DBMS-sätt att göra det på. För MySQL och Oracle visas bara det enkla heltalstestet; för SQL Server visas det fullständiga numeriska testet.
För SQL Server:observera att isnumeric('.') returnerar 1.. men det kan faktiskt inte konverteras till float. Viss text som "1e6" kan inte konverteras till numerisk direkt, men du kan passera genom float, sedan numerisk.
;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
För 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
För Oracle
case when REGEXP_LIKE(col, '[^0-9]') then col*1 end