select a,b,null,null from table1 union select null,null,c,d from table2 union select null,null,null,null,e,f from table3.
Then in the second table I have select ..., null as opt from... I know that I could have an empty string with '' as
The Background I was trying to solve the fourth realistic mission in hackthissite.org, and couldn't figure out exactly what SQL I should inject into the URL to retrieve the list of emails.
Union select null, null, null, null, null, null, null from information_schema.tables. for a small database containing three tables. this instruction is used in sql injection I tried it and it worked but I didn't really know how it works can somebody help me...
select cast (2000 as type of quint) from rdb$database select cast (2000 as int) from rdb$database.
Note: A NULL value is different from a zero value or a field that contains spaces.
What is the difference between … and … and why does the latter not work?
union all select null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null
Даже выражение NULL != NULL не будет истинным, ведь нельзя однозначно сравнить одну неизвестность с другой. Кстати, ложным это выражение тоже не будет, потому что при вычислении условий Oracle не ограничивается состояниями ИСТИНА и ЛОЖЬ.
R language supports several null-able values and it is relatively important to understand how these values