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.
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...
Postgres is the database Can I use a NULL value for a IN clause? example: … I want to limit to these four values. I have tried the above statement and it doesn't work...
SELECT COUNT(*), 'null_tally' AS narrative FROM us WHERE a IS NULL UNION SELECT COUNT(*), 'not_null_tally' AS narrative
The Background I was trying to solve the fourth realistic mission in hackthissite.org, and couldn't figure out exactly what SQL I should inject into the URL to retrieve the list of emails.
What is the difference between … and … and why does the latter not work?
Above is two queries with their results merged by a UNION ALL clause. You will notice that the queries return different columns, one called 'departure' and one called 'arrival'.
A field with a NULL value is a field with no value. If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to this
In SQL, the NULL value is never true in comparison to any other value, even NULL. An expression that contains NULL always produces a NULL value unless otherwise indicated in the documentation for the operators and functions involved in the expression. All columns in the following example return NULL
SQL’s NULL indicates absent data. NULL propagates through expressions and needs distinct comparison operators.