select every other row in MySQL without depending on any ID?

Question

Considering following table that doesn\'t have any primary key, can I select every other row?

col1      col2
 2         a
 1         b
 3         c
 12               


        

Answer 1

Try this. I've adapted it from the answer linked below. I tested it on SQLFiddle and it appears to work.

http://sqlfiddle.com/#!2/0bccf/28
http://sqlfiddle.com/#!2/0bccf/29

Odd Rows:

SELECT x.*
FROM (
     SELECT @rownum:=@rownum+1 rownum, t.*
     FROM (SELECT @rownum:=0) r, table t
) x
WHERE MOD(x.rownum, 2) = 1

Even Rows:

SELECT x.*
FROM (
     SELECT @rownum:=@rownum+1 rownum, t.*
     FROM (SELECT @rownum:=0) r, table t
) x
WHERE MOD(x.rownum, 2) = 0

Adapted from: MySQL row number