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.
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...
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.
How does UNION handle NULL values, and how does GROUP BY handle NULL values? EDIT: I changed the second query (the second column was wrong). EDIT2: Thanks for the answer, but could you explain what's the difference? I thought that it might be because of...
Then in the second table I have select ..., null as opt from... I know that I could have an empty string with '' as opt however, I
Предикат IS NULL позволяет проверить отсутствие (наличие) значения в полях таблицы. Использование в этих случаях обычных предикатов сравнения может привести к неверным результатам, так как сравнение со значением NULL дает...
Above is two queries with their results merged by a UNION ALL clause. You will notice that the queries return different columns, one called 'departure' and one called 'arrival'.
I have come across some code that says … What exactly is this doing? Is it getting the field names unitcost and markup? Why would you use "select null as..."? New to this sorry.
What is the difference between … and … and why does the latter not work?
Note: A NULL value is different from a zero value or a field that contains spaces. A field with a NULL value is one that has been left