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, 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...
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.
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Обработка... Не сейчас. Месяц бесплатно. SGs2 imei (null null) решение проблемы.
What is the difference between … and … and why does the latter not work?
E.g. null + null + 1 = 1 null + null + null = null. The problem is that the first expression yields null.
The IS NOT NULL condition is used in SQL to test for a non-NULL value. It returns TRUE if a non-NULL value is found, otherwise it returns FALSE.
NULL is a special value that signifies 'no value'. Comparing a column to NULL using the = operator is undefined. Instead, use WHERE IS NULL or WHERE
NULL is special in SQL. NULL indicates that the data is unknown, inapplicable or even does not exist. In other words, NULL represents that the data is missing in the database. For example, if an employee does not have any phone number, you can store it as an empty string.