单行mysql中的多行

Question

嘿伙计们我陷入了凌乱的结构，在编写查询时需要帮助，这是我当前的查询

SQL：

SELECT  `name` , trnid,  `material` , SUM( quantity )qty , SUM( price ) price, SUM( preturn ) return 
FROM  `transactions` a
JOIN item_master b ON a.material = b.id
GROUP BY material, trnid
LIMIT 0 , 30

输出：

如果你看到上面有相同材料的2条记录（trnd 1是购买数量＆amp; trnd 2是问题数量）我希望这些是具有以下列的单条记录。

名称|材料| purqty | issqty

Answer 1

我认为你想要条件聚合：

SELECT  name, material,
        SUM(case when trnid = 1 then quantity else 0 end) as purchaseqty,
        SUM(case when trnid = 2 then quantity else 0 end) as issueqty
FROM transactions t JOIN
     item_master im
     ON t.material = im.id
GROUP BY name, material
LIMIT 0 , 30;