SQL Server Data Type traps

1.

Bit type: bit (1) don't think it's just a bit, in fact it's going to take up a byte! That means when n < 8 o'clock is like this!

2.

varchar (n) here n cannot be greater than 8000, if you want to be larger than 8000 you can only specify varchar (max); Here's the same for nvarchar (n).

What I don't understand is why 8000 is not 2 of the 16-time party! Why Max can be infinitely big!

3.

Sql_variant can think of it as an object type in C#/java, that is to say what objects can exist inside, attention is also required, objects can not exceed 8000 bytes!

Don't think you know this is no matter, there are many things!

Example:

CREATE table t (x sql_variant);

INSERT into t (x) values (1234); can perform

INSERT into t (x) VALUES (' ABCD '); can perform

INSERT into t (x) VALUES (1234), (' ABCD '); You cannot execute the hint "failed while converting varchar value ' ABCD ' to data type int"

4.

FileStream table to have a column of uniqueidentifier columns, and requires that it is not NULL, unique!

SQL Server Data Type traps