So the expressions ISNULL(NULL, 1) and COALESCE(NULL, 1) although equivalent have different nullability values. This makes a difference if you
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.
SELECT * FROM `mydata`.`mytable` WHERE CONCAT(<list of columns>) IS NOT NULL.
By specifically mentioning NULL pointer, C standard gives mechanism using which a C programmer can use and check whether a given pointer is legitimate or not.
CONCAT_NULL_YIELDS_NULL ON INSERT INTO Mytable(StringValue) SELECT COALESCE
The reasoning is that a null means "unknown", so the result of any comparison to a null is also "unknown". So you'll get no hit on rows by coding where my_column = null. SQL provides the special syntax for testing if a column is null, via is null and is not null, which is a special condition to test for a...
Команда IS NOT NULLпроверяет поле на не NULL.