Question

I understand

SELECT * FROM T WHERE C1 = 1;

But I don’t fully understand

SELECT * FROM T MyT WHERE MyT.C1 = 1;

What is MyT?

Answer 1

MyT is an alias for that reference of the table.

SELECT * FROM T MyT WHERE MyT.C1 = 1;

will work as well as

SELECT * FROM T MyT WHERE C1 = 1;

which will work as well as

SELECT MyT.FieldName FROM T MyT WHERE MyT.C1 = 1;

But this won’t work:

 SELECT T.FieldName FROM T MyT WHERE MyT.C1 = 1;

You must use the alias to refer to the table after it is assigned.

These are essential when joining a table to itself:

 SELECT *
 FROM
   T MyT INNER JOIN
   T MyT2
     ON MyT.ManagerID = MyT2.EmployeeID
 WHERE MyT.C1 = 1;