MySQLの結果の半分

Question

で、私はこの

item qty rate item1 qty1 rate1 
==================================== 
test1 10 22 test2 16 26 
test3 11 25 test4 16 26 
test5 12 22 test6 16 26 
test7 14 50 test8 16 26 

または

item qty rate item1 qty1 rate1 
    ==================================== 
    test1 10 22 test5 12 22 
    test2 16 26 test6 16 26 
    test3 11 25 test7 14 50 
    test4 16 26 test8 16 26 

ようにしたい半分に私の結果を分割し、行この

メイン表のようになりました

item qty rate 
=============== 
test1 10 22 
test2 11 25 
test3 12 22 
test4 14 50 
test5 16 26 
test6 55 20 
test7 60 60 

を追加したいです

Answer 1

サイズによっては時間がかかりますテーブルの解決策は...

SELECT ROUND(COUNT(*)/2) INTO @cnt FROM tobehalf; 

SELECT t1.item, t1.qty, t1.rate, t2.item as item1, t2.qty as qty1, t2.rate as rate1 FROM 
(
SELECT * FROM (SELECT tobehalf.*, @rownum1 := @rownum1 + 1 AS rank 
FROM tobehalf, (SELECT @rownum1 := 0) r1) d1 
WHERE d1.rank <= @cnt 
) t1 
LEFT JOIN 
(
SELECT * FROM (SELECT tobehalf.*, @rownum2 := @rownum2 + 1 AS rank 
FROM tobehalf, (SELECT @rownum2 := 0) r2) d2 
WHERE d2.rank > @cnt 
) t2 on t1.rank = t2.rank - @cnt