Question

我需要什么

我有一个名为dbtuts的数据库，它共有7个表。

表名是tbl_uploads，variationtable1，variationtable2，variationtable3，variationtable4，variationtable5，variationtable6。

所有这些表都有一个名为prjId的列。

我想从tbl_uploads表中删除一行，并从variationtable1删除到variationtable6，其中prjId可以说是xxxx。

但问题是变化可变1到变化表6可能有也可能没有prjId列的xxxx数据。

有没有办法可以执行单个查询，如果有这样的数据就会删除xxxx。

我的代码

我尝试按以下方式操作，但它无效。

$deleteQuery = "
DELETE 
  FROM dbtuts.tbl_uploads
     , dbtuts.variationtable1
     , dbtuts.variationtable2
     , dbtuts.variationtable3
     , dbtuts.variationtable4
     , dbtuts.variationtable5
     , dbtuts.variationtable6 
 WHERE prjId = 'xxxx'
 ";

$resultDeleteQuery = mysqli_query($conn,$deleteQuery);

有没有人有想法？

Answer 1

您可以使用LEFT JOIN进行单个查询：

DELETE t, v1, v2, v3, v4, v5, v6
  FROM dbtuts.tbl_uploads t
  LEFT JOIN dbtuts.variationtable1 v1 ON t.prjId = v1.prjId
  LEFT JOIN dbtuts.variationtable2 v2 ON t.prjId = v2.prjId
  LEFT JOIN dbtuts.variationtable3 v3 ON t.prjId = v3.prjId
  LEFT JOIN dbtuts.variationtable4 v4 ON t.prjId = v4.prjId
  LEFT JOIN dbtuts.variationtable5 v5 ON t.prjId = v5.prjId
  LEFT JOIN dbtuts.variationtable6 v6 ON t.prjId = v6.prjId
WHERE t.prjId = 'xxxx'

Demo here

注意：如果您的数据库架构设计得当，那么这种查询就不是必需的。实现这种功能的正确方法是使用dbtuts.variationtablex在每个ON CASCADE DELETE表中创建外键。

Answer 2

这将是最简单的方法，并在1个查询中

$deleteQuery = "DELETE FROM dbtuts.tbl_uploads WHERE prjId = 'xxxx';
                DELETE FROM dbtuts.variationtable1 WHERE prjId = 'xxxx';
                DELETE FROM dbtuts.variationtable2 WHERE prjId = 'xxxx';
                DELETE FROM dbtuts.variationtable3 WHERE prjId = 'xxxx';
                DELETE FROM dbtuts.variationtable4 WHERE prjId = 'xxxx';
                DELETE FROM dbtuts.variationtable5 WHERE prjId = 'xxxx';
                DELETE FROM dbtuts.variationtable6 WHERE prjId = 'xxxx'";

请记住在执行此查询时使用预准备语句，以防止您的项目遭到SQL注入 - 感谢Strawberry提及你可以这样做

$stmt = $mysqli->prepare("DELETE FROM dbtuts.tbl_uploads WHERE prjId = 'xxxx';
                          DELETE FROM dbtuts.variationtable1 WHERE prjId = 'xxxx';
                          DELETE FROM dbtuts.variationtable2 WHERE prjId = 'xxxx';
                          DELETE FROM dbtuts.variationtable3 WHERE prjId = 'xxxx';
                          DELETE FROM dbtuts.variationtable4 WHERE prjId = 'xxxx';
                          DELETE FROM dbtuts.variationtable5 WHERE prjId = 'xxxx';
                          DELETE FROM dbtuts.variationtable6 WHERE prjId = 'xxxx'";);
$stmt->execute(); 
$stmt->close();

如何在一个删除查询中使用多个表名 - 并非所有表都包含数据

2 个答案: