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...
Then in the second table I have select ..., null as opt from... I know that I could have an empty string with '' as
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.
ID in both tables will never be NULL. It IS possible that one of the tables may have ID values that are NOT in the other table.
The null character (also null terminator or null byte), abbreviated NUL or NULL, is a control character with the value zero. It is present in many character sets, including ISO/IEC 646 (or ASCII)...
R language supports several null-able values and it is relatively important to understand how these values behave, when making data pre-processing and
NULL is special in SQL. NULL indicates that the data is unknown, inapplicable or even does not
Instead, use WHERE IS NULL or WHERE IS NOT NULL. The definitive guide for data professionals. See 2 min video.