Question

I would like to know how MySQL interprets the CREATE TABLE syntax:

If I write:

CREATE TABLE tbl1 (
    `v1` int,
    `v2` int
     CONSTRAINT idx PRIMARY KEY (v1)
)
SELECT a, b FROM tbl2;

• Does it determine which value goes into v1 and which goes into v2
  by their order in the select statement?

• Does it use the names I designate in the CREATE TABLE statement or
  does it take them from the select statement?

I have used the CREATE TABLE XX SELECT val FROM YY before but would like to know more specifically about the above syntax.

Answer 1

With your current solution you’ll get a table with the columns v1, v2, a, and b.

To see how it is done properly, see the "CREATE TABLE … SELECT Statement" chapter in the official MySQL documentation.

So if you just want v1 and v2 with an index on v1, do it like this:

CREATE TABLE tbl1 (PRIMARY KEY (v1))
SELECT a v1,
       b v2
FROM tbl2;