Question

我想用列handleMouseDown = event => { this.setState({ dragging: true, dragStart: event.screenX, }); }; handleMouseUp = () => { this.setState({ dragging: false }); }; handleMouseMove = event => { if (this.state.dragging) { const position = event.screenX; // <-- update your image index } }; render = () => { return ( <div onMouseDown={this.handleMouseDown}> {this.renderImage()} </div> ); }; componentDidMount = () => { document.addEventListener('mousemove', this.handleMouseMove, false); document.addEventListener('mouseup', this.handleMouseUp, false); }; componentWillUnmount = () => { document.removeEventListener('mousemove', this.handleMouseMove, false); document.removeEventListener('mouseup', this.handleMouseUp, false); };的值更新列created_at的值，其中列updated_at的值是 0000-00-00 。

我尝试了以下查询：

created_at

但是查询结果如下：

UPDATE tbl_message_types a 
SET a.created_at = (
SELECT
    c.updated_at 
FROM
    ( SELECT b.updated_at 
      FROM tbl_message_types b 
      WHERE b.created_at LIKE '%0000-00-00%' 
        AND a.id = c.id ) AS c 
    ) 
    AND a.created_at LIKE '%0000-00-00%';

如何修改查询？

Answer 1

您的别名不适当，但是我会使用连接来表达此更新：

UPDATE tbl_message_types a
INNER JOIN UPDATE tbl_message_types b
    ON a.id = b.id AND
       COALESCE(b.created_at, '0000-00-00') != '0000-00-00'
WHERE COALESCE(a.created_at, '0000-00-00') = '0000-00-00';

请注意，您不清楚表中的日期时间值如何为0000-00-00。我会以同样的方式对待NULL，尽管如果您不同意也可以删除对COALESCE的呼叫。

Answer 2

我认为您可以以非常简化的方式来完成此操作。为什么要坚持一个查询..？首先选择，然后更新。试试这个。

     select 

        value1 from tableName 

        where columnX like '%someThing%' and columnY = 'SomeValue' as value11;

     update sametableName set someColumn= value11

         where....

使用同一表列行中的值更新表行

2 个答案: