Question

我在一个名为height的varchar字段中存储了一些浮动数字格式，如1.30，然后我想按高度查找数据，所以我正在使用

<p:ajax event="rowDblselect" update=":form" oncomplete ="PF('table').filter();"/>

来查询。但没有回来。然后我想也许我应该用float查询，所以我将SQL改为

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
    at sun.reflect.GeneratedConstructorAccessor14.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1127)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:356)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2502)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2539)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2321)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:832)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
    at sun.reflect.GeneratedConstructorAccessor11.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:417)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:344)
    at java.sql.DriverManager.getConnection(DriverManager.java:571)
    at java.sql.DriverManager.getConnection(DriverManager.java:187)
    at org.logicalcobwebs.proxool.DefaultConnectionBuilder.buildConnection(DefaultConnectionBuilder.java:39)
    at org.logicalcobwebs.proxool.Prototyper.buildConnection(Prototyper.java:159)
    at org.logicalcobwebs.proxool.Prototyper.sweep(Prototyper.java:102)
    at org.logicalcobwebs.proxool.PrototyperThread.run(PrototyperThread.java:44)
Caused by: java.net.ConnectException: Connection refused
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.j

并得到了正确的结果。

怎么会发生这种情况？我的意思是，当在varchar字段中浮动的商店时发生了什么。

Answer 1

您的varchar列可能有一些前导或尾随空格。如果将decimal存储为varchar并放置前导或尾随空格，那么您的搜索条件将永远不会满足。因此' 1.30'不能等于'1.30'。

但是，如果你只比较它1.30，那么mysql首先投射它并进行比较。因此，你得到了结果。（这就是我的想法。如果我错了，请纠正我

请参阅以下示例

http://sqlfiddle.com/#!9/503c2/1

MySQL-Store浮点数在varchar字段中无法找到？

1 个答案: