Question

我需要删除目标表中存在但源表中没有的记录。目标表中的主键是源表中不存在的auto_increment ID。源表和目标表都包含一组唯一的键组合，可用于唯一地标识两个表中的行。我应该遵循什么方法？如果我要使用多个列组合作为唯一键而不是一个主键（源代码中不存在），该如何删除？

 delete from dest_table
 where (uniq_key_col1,uniq_key_col2) not in (
   select dest.uniq_key_col1,dest.uniq_key_col2 
   from dest_table dest
   join source_table source
   on dest.uniq_key_col1=source.uniq_key_col1
   and dest.uniq_key_col2=source.uniq_key_col2
 )

这是理想的外观（出于清楚起见而提供，由于多列，请忽略where子句中的错误）

Answer 1

您可以使用存在。即：

delete from dest_table
 where not exists (
   select * 
   from source_table source
   where dest_table.uniq_key_col1=source.uniq_key_col1
   and dest_table.uniq_key_col2=source.uniq_key_col2
 );

Answer 2

您可以这样：

DELETE
FROM dbo.dest a 
WHERE NOT EXISTS (
      SELECT 1
        FROM dbo.source1 b
       WHERE a.id1 = b.ID1 and a.id2 = b.id2
      )

Answer 3

另一个适合您的选择

class App extends Component {
  constructor(props) {
    super(props);
    const { pathname } = this.props.location;
    this.state = {
      isNavbarHidden: pathname === "/" || pathname === "/Register"
    };
  }

  componentDidMount() {
    this.unlisten = this.props.history.listen(location => {
      const { pathname } = location;
      const isNavbarHidden = pathname === "/" || pathname === "/Register";

      this.setState({ isNavbarHidden });
    });
  }

  componentWillUnmount() {
    this.unlisten();
  }

  render() {
    const { isNavbarHidden } = this.state;

    return (
      <div>
        {!isNavbarHidden && <Navigation />}
        <Link to="/">Login</Link>
        <Link to="/Register">Register</Link>
        <Link to="/Home">Home</Link>
        <Link to="/Dashboard">Dashboard</Link>
        <div className="sans-serif">
          <Route exact path="/" component={Login} />
          <Route exact path="/Register" component={Register} />
          <Route exact path="/Home" component={Home} />
          <Route exact path="/Dashboard" component={Dashboard} />
        </div>
      </div>
    );
  }
}

ReactDOM.render(
  <BrowserRouter>
    <Route path="/" component={App} />
  </BrowserRouter>,
  document.getElementById("root")
);

Answer 4

听起来好像不需要EXISTS

DELETE d FROM dest_table d 
WHERE NOT EXISTS (SELECT (PUT_APPROPRIATE_COLUMNS_HERE) from source_table s 
   WHERE d.col1 = s.col
   AND d.col2 = s.col2
   ... etc for other columns
   )

请注意表别名，您需要这样做。如果可能的话，使用内部联接可能更合适。

删除SQL Server中的功能增量负载

4 个答案: