Question

我希望将两个表连接到临时表中，然后在选择查询中使用临时表。这是我要创建的临时表的select语句：

rails generate

为上述方法创建临时表的最简单方法是什么？

Answer 1

您可以创建一个临时表（您可能想要），但如果您还不知道，我想指出您可以在这样的查询中创建虚拟临时表

SELECT * 
FROM (
  select program, event
  from OMEGA.HP
  inner join POM.GT on program = substring(name,7,4)
  where LENGTH(name)= 25
) AS Virtual_table

你甚至可以像这样加入其中一个表：

SELECT * 
FROM (
  select program, event
  from OMEGA.HP
  inner join POM.GT on program = substring(name,7,4)
  where LENGTH(name)= 25
) AS v_table74
join (
  select program, event
  from OMEGA.HP
  inner join POM.GT on program = substring(name,2,5)
  where LENGTH(name)= 25
) as v_table25 on v_table74.program = v_table25.program

Answer 2

select program, event
into #temp    --------------------------------check here
from OMEGA.HP
inner join POM.GT
on program = substring(name,7,4)
where LENGTH(name)= 25

Answer 3

使用公用表表达式（CTE）：

class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout {

@objc(collectionView:layout:sizeForItemAtIndexPath:)
func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    sizeForItemAt indexPath: IndexPath) -> CGSize {

    let flowLayout = collectionViewLayout as! UICollectionViewFlowLayout
    let totalSpace = flowLayout.sectionInset.left
        + flowLayout.sectionInset.right
        + (flowLayout.minimumInteritemSpacing * CGFloat(4 - 1))
    let size = Int((collectionView.bounds.width - totalSpace) / CGFloat(4))
    return CGSize(width: size, height: size)
}
}

SQL - 创建连接的临时表

3 个答案: