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分享java sql为什么会报错
String str = "";
conn = DBHelper.getConn();
try
{
ps = conn.prepareStatement("select (select b.Name from Permission b where b.ID=a.PermissionID) name from UserAccountXPermission a where a.UserAccountID = (select ID from UserAccount where UserName=?)");
ps.setString(1, ua.getUsername());
rs = ps.executeQuery();
str = rs.getString("name");
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
DBHelper.close(conn, ps, rs);
}
return str;为什么执行这条语句会报错 不能执行这么长的吗？还是其他方法
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n27741 2013-06-24
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Before start of result set
记录指针位置在记录头，要Next一下
ffc253605481 2013-06-24
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SQL语句直接写错了..
nongzhenqin 2013-06-24
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SQL语句有问题。
myisfei 2013-06-23
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是result没有打开，
rs = ps.executeQuery();
rs.next();
str = rs.getString("name");
程序员A 2013-06-23
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执行完sql语句后,ResultSet 对象的游标是指向第0行的，当你调用一次rs.next()时，就往下移动，变成1，你取数据是从第1行开始的，所以你在真正调用rs.getString()之前一定要调用rs.next()方法，如果不调用的话，rs.getString取的就是第0行，肯定会有问题的。
「已注销」 2013-06-20
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Bettygonna 2013-06-19
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会不会是根本没有连接上数据库
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
sanfan0819 2013-06-19
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sql语句的问题，你最后是得到哪张表中的name ,如果是由条件得到 Permission表中的name,那么
sql= select Name from Permission where ID=(select PermissionID from serAccountXPermission where UserAccountID=(select ID from UserAccount where UserName=?))
SorrowEnding 2013-06-19
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不知道怎么写好点。。能指教下吗[/quote]
什么意思？
结果集一行的话，
直接
rs = ps.executeQuery();
rs.next();//加上这一句
str = rs.getString("name");
多行就像上面一样，用while[/quote]
我指的是那个sql语句啊~
菖蒲老先生 2013-06-19
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不知道怎么写好点。。能指教下吗[/quote]
什么意思？
结果集一行的话，
直接
rs = ps.executeQuery();
rs.next();//加上这一句
str = rs.getString("name");
多行就像上面一样，用while
SorrowEnding 2013-06-19
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不知道怎么写好点。。能指教下吗
菖蒲老先生 2013-06-19
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rs = ps.executeQuery();
while(rs.next()){
str = rs.getString("name");
}
跟sql没关系么，虽然sql写法有点。。。
火影之贺 2013-06-19
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select (select 这里明显语法错误！
SorrowEnding 2013-06-19
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java.sql.SQLException: Before start of result set
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:910)
at com.mysql.jdbc.ResultSet.checkRowPos(ResultSet.java:720)
at com.mysql.jdbc.ResultSet.getStringInternal(ResultSet.java:5624)
at com.mysql.jdbc.ResultSet.getString(ResultSet.java:5544)
at com.mysql.jdbc.ResultSet.getString(ResultSet.java:5584)
at Handler.UserAccountHandler.checkUser(UserAccountHandler.java:48)
at UI.LoginUI$Monitor.actionPerformed(LoginUI.java:72)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
SorrowEnding 2013-06-19
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我的UserAccountXPermission 没有name的啊~只有UserAccountID和PermissionID ，Permisson表里才有name 我在数据库里运行可以的。但是程序就报错
ydb7459022 2013-06-19
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报什么错都不贴出来，怎么看！！
「已注销」 2013-06-19
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select (select b.Name from Permission b where b.ID=a.PermissionID) name from UserAccountXPermission a where a.UserAccountID = (select ID from UserAccount where UserName=?)
这句sql错了
换成
select name from UserAccountXPermission a where a.UserAccountID = (select ID from UserAccount where UserName=?)
试试
rumlee 2013-06-19
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把语句直接在数据库里面执行一下看看报告什么错误啊，或者看在程序里面执行抛出什么异常啊。
肯定不是因为不能执行这么长的，你这语句也叫长啊，很短的了。
