mysql insert + select row_id

Question

Suppose I have two table:

create table ladder (
      user_id INT UNSIGNED NOT NULL PRIMARY KEY
     , rank INT UNSIGNED NOT NULL UNIQUE
     );

create table myuser (
      user_id INT UNSIGNED NOT NULL PRIMARY KEY
     , rating INT UNSIGNED NOT NULL
);

myuser consists of a rating, where higher rating represent a better user. ladder is the ranking table, rank is range from 1, 2,3, 4, 5... where the user_id with rank=1 has the highest rating.

ok, when i do an INSERT + SELECT :

DELETE FROM ladder;  -- clean the table first
INSERT INTO ladder (user_id, rank) SELECT user_id, XXX FROM myuser ORDER BY rating;

then I need something like XXX represent the ROW id of the SELECT myuser, so that XXX = 1 for the first row, 2 for the second row.

is this possible ?

(or XXX = 0 for the first row, and i will do XXX+1 in select)

Answer 1

There is no such ROW_NUM in MySQL . Generate it while running the SELECT statement and use.

Example :

INSERT INTO ladder (user_id, rank) 
  SELECT 
    user_id, @r:=(@r + 1 ) 
  FROM 
    myuser,
    ( SELECT @r:=0 ) 
  ORDER BY rating;

Demo : Example @ SQL Fiddle