Select char_length(cast('123456789 1' as varchar(10))) from rdb$database. Получаем: Exception ... string truncation Т.е. пробел мы обрезать можем, а другие символы нет. Так и должно быть или нет?
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...
The null character (also null terminator or null byte), abbreviated NUL or NULL, is a control character with the value zero.
union all select null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null
As a result, they just used `NULL values to populate those columns. the real confusion is in the CONCAT(). They are combining 126, 39, database name as hex
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 blank during record creation!
Union select null, null, null, null, null, null -- test all nulls --*/ ). A. DECLARE @ColumnDynamicSQL nvarchar(MAX)
Nulls can appear in columns of any datatype that are not restricted by NOT NULL or PRIMARY KEY integrity constraints.
In general, R supports: NULL NA NaN Inf / -Inf NULL is an object and is returned when an expression or function results in an undefined value.