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.
Then in the second table I have select ..., null as opt from... I know that I could have an empty string with '' as opt however, I
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...
How can I run a MySQL query that selects everything that is not null? It would be something like … Do I just remove the all and go..?
union all select null,null,null,null,null,null,null,null,null,null,null,null,null,null,null
What is the difference between … and … and why does the latter not work?
Note: not a NULL field value, but the null character (see link). I have a column with a mix of typical and a null character. I'm trying to replace the null character with a different value. I would have thought that the following would work but it is unsuccessfull
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
I ran into code similar to this today. … It seems to imply that data type information can be associated with a NULL value. Does this attach metadata to the NULL value identifying it as the specified data...
Предикат IS NULL позволяет проверить отсутствие (наличие) значения в полях таблицы. Использование в этих случаях обычных предикатов сравнения может привести к неверным результатам, так как сравнение со значением NULL дает...