Question

这是代码。有人可以解释一下gi和ogi在此声明中的含义吗？

UPDATE `oceansne_website08`.`oc_gallery_image_description` ogi
LEFT Join  `gallery_image_to_album` gi ON gi.image_id = ogi.gallery_image_id
SET
`gallery_album_id` = gi.album_id
WHERE ogi.gallery_album_id =0;

Answer 1

它是一个别名；在您的示例中引用表的简化形式。

   UPDATE `oceansne_website08`.`oc_gallery_image_description` ogi
LEFT JOIN `gallery_image_to_album` gi 
       ON gi.image_id = ogi.gallery_image_id
      SET `gallery_album_id` = gi.album_id
    WHERE ogi.gallery_album_id =0

此处ogi引用了表-> oceansne_website08。oc_gallery_image_description gi指向表格-> gallery_image_to_album

Answer 2

让我们说您有一个名为MyVeryLongTableNameThatIFindTediousToWrite的表，并且您希望将其连接到MyEvenLongerAndMoreTediousTableWithAnEvenLongerName

您可以写：

SELECT * FROM mydb.MyVeryLongTableNameThatIFindTediousToWrite 
INNER JOIN  myotherdb.MyEvenLongerAndMoreTediousTableWithAnEvenLongerName 
ON mydb.MyVeryLongTableNameThatIFindTediousToWrite.id = myotherdb.MyEvenLongerAndMoreTediousTableWithAnEvenLongerName.otherId 
WHERE myotherdb.MyEvenLongerAndMoreTediousTableWithAnEvenLongerName.value > 100

要使其更清晰易懂，您可以使用别名，因此相同的选择可以写为：

SELECT * FROM mydb.MyVeryLongTableNameThatIFindTediousToWrite tbla
INNER JOIN  myotherdb.MyEvenLongerAndMoreTediousTableWithAnEvenLongerName  tblb
ON tbla.id = tblb.otherId 
WHERE tblb.value > 100

在某些SQL风格中，您需要编写mydb.MyVeryLongTableNameThatIFindTediousToWrite AS tbla来代替，但这对于此答案来说有点题外话了

此SQL语句中的ogi和gi是什么意思

2 个答案: