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...
Note: A NULL value is different from a zero value or a field that contains spaces.
Select * from(select driverid, name, ssn from drivers where driverid<15 UNION ALL Select driverid,name, cast(null as bigint) from drivers where driverid BETWEEN 18 AND 21) T ; SemanticException 3:48 Schema of both sides of union should match.
E.g. null + null + 1 = 1 null + null + null = null. The problem is that the first expression yields null.
R language supports several null-able values and it is relatively important to understand how these
The IS NOT NULL condition is used in SQL to test for a non-NULL value.
The NOT NULL constraint specifies that NULL is not an allowable value. For example, in the following statement, CREATE TABLE Customer (SID integer NOT NULL
Null (or NULL) is a special marker used in Structured Query Language to indicate that a data value does not exist in the database. Introduced by the creator of the relational database model, E. F. Codd...