无法识别以下函数中的SQL语法错误：导致例外

Question

我不断收到以下错误。

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: 
You have an error in your SQL syntax; check 
the manual that corresponds to your MySQL server version for 
the right syntax to use near '= 3' at line 1 

我通过我的整个代码去了，只有它被称为在这个时间点2个SQL函数，能够引起这种错误的：

1. 读

   public void Read (String userName) /*have checked validity*/ 
   try { 
       con = getConnection(); 
   
       PreparedStatement pstmt = con.prepareStatement("SELECT * FROM " + 
              tableName + 
             " WHERE userName=?"); 
   
        pstmt.setString(1,userName); 
   
       ResultSet rs = pstmt.executeQuery(); 
   
       User user; 
       PrintQuery(rs); 
       rs.close(); 
       pstmt.close(); 
       releaseConnection(con); 
       return user; 
   
   } 
   

2. GetItem

   public void getItem(int userid) /*have checked validity*/ 
   try { 
       con = getConnection(); 
   
       Statement stmt = con.createStatement(); 
   
       PreparedStatement pstmt = con.prepareStatement("SELECT * FROM " 
              + tableName +"WHERE UserId=?"); 
       pstmt.setInt(1,userid); 
       rs = pstmt.executeQuery(); 
       PrintQuery(rs); 
       stmt.close(); 
       releaseConnection(con); 
   
   } 
   

我被困在这些小时现在，我无法解决它。我有双重检查，看看这些参数是否为空等，他们不是。事实上，它们都很好地存在于数据库中。我无法弄清楚我哪里出错了。任何帮助都感激不尽。

Answer 1

错误是GetName因为你的表名和WHERE条款

+ tableName +" WHERE UserId=?"); 
      //^add extra space here