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...
Используйте NULL в UNION-инъекциях вместо попыток угадать строку, дату, число и прочее. Но будьте аккуратны при слепой инъекции, т.к. вы можете спутать ошибку БД и самого приложения. Некоторые языки, например ASP.NET, выдают ошибку при использовании значения NULL (т.к...
The IS NULL operator is used to test for empty values (NULL values). The following SQL lists all customers with a NULL value in the "Address" field: Example. SELECT CustomerName, ContactName, Address FROM Customers WHERE Address IS NULL
Select Group, Count(*) From [Data] Group by [Group]. The reason null shows 0 instead of 2 in this case is because each cell is counted as either 1 or null and null + null = null so the total of that group would also be null. However the column type is an integer so it shows up as 0.
IS NULL вернёт истину, если операнд имеет значение NULL и ложь, если он им не является.
NULL в языках программирования Си и C++ — макрос, объявленный в заголовочном файле stddef.h (и других заголовочных файлах).
Значение Null не является ни пустой строкой (для символьного типа данных или типа данных datetime), ни нулевым значением (для
The null character (also null terminator or null byte) is a control character with the value zero. It is present in many character sets, including ISO/IEC 646 (or ASCII), the C0 control code, the Universal Coded Character Set (or Unicode), and EBCDIC.
I have the following query that may return null if certain dates are selected, I want to display 0 instead of a blank but cannot figure it out: * I removed the date code to make it easier. SELECT ISNULL(COUNT(*), '0') AS thecount.
SQL> select count(*) from chr where x is null