通过Java连接到MySQL时的SQL语法错误

Question

我通过Java使用以下代码连接到数据库。

import java.sql.*; 

public class Can { 

//Database Credentials 
private static String userName = "root"; 
private static String password = "root"; 
private static String databaseName = "books"; 

static Connection connection = null; // manages connection 
static Statement statement = null; // query statement 
static ResultSet resultSet = null; // manages results 

static Can can; 


public static void main(String[] args) { 

    can = new Can(); 
    ResultSetMetaData metaData; 
    int numberOfColumns; 


    try { 
     connection = DriverManager.getConnection("jdbc:mysql://localhost/"+databaseName, userName, password); 
     statement = connection.createStatement(); 
     connection.setAutoCommit(false); 

     //creating the tables 
     statement.executeUpdate("CREATE TABLE Instructor" + "(instructorID INT, instructorName VARCHAR(30), PRIMARY KEY (instructorID))"); 
     statement.executeUpdate("CREATE TABLE Lecture" + "(lectureID INT, lectureName VARCHAR(30), time TIME, credit INT, instructorID INT, PRIMARY KEY (lectureID))"); 
     statement.executeUpdate("CREATE TABLE LectureStudent" + "(lectureID INT, studentID INT, PRIMARY KEY (lectureID, studentID))"); 
     statement.executeUpdate("CREATE TABLE Student" + "(studentID INT, studentName VARCHAR(30), CGPA FLOAT, PRIMARY KEY (studentID))"); 
     statement.executeUpdate("CREATE TABLE Assignment" + "(assignmentID INT, deadline INT(30), lectureID INT, PRIMARY KEY (assignmentID))"); 
     statement.executeUpdate("CREATE TABLE Results" + "(resultID INT, grade FLOAT, PRIMARY KEY (resultID)"); 


     //inserting info. into the tables 
     statement.executeUpdate("INSERT INTO Instructor VALUES('1', 'instructorName1')"); 
     statement.executeUpdate("INSERT INTO Instructor VALUES('2', 'instructorName2')"); 

     statement.executeUpdate("INSERT INTO Lecture VALUES('1', 'lectureName1', '20:16:40', '3', '1')"); 
     statement.executeUpdate("INSERT INTO Lecture VALUES('2', 'lectureName2', '20:33:20', '4', '1')"); 
     statement.executeUpdate("INSERT INTO Lecture VALUES('3', 'lectureName3', '20:33:25', '4', '2')"); 

     statement.executeUpdate("INSERT INTO LectureStudent VALUES('1', '100')"); 
     statement.executeUpdate("INSERT INTO LectureStudent VALUES('2', '100')"); 
     statement.executeUpdate("INSERT INTO LectureStudent VALUES('3', '100')"); 

     statement.executeUpdate("INSERT INTO Student VALUES('100', 'studentName1', '2.4')"); 
     statement.executeUpdate("INSERT INTO Student VALUES('200', 'studentName2', '2.5')"); 
     statement.executeUpdate("INSERT INTO Student VALUES('300', 'studentName3', '2.6')"); 

     statement.executeUpdate("INSERT INTO Assignment VALUES('1000', '1969-12-31 10:40:00.0', '1')"); 

     statement.executeUpdate("INSERT INTO Results VALUES('1', '90.0')"); 


     //commit the transaction 
     connection.commit(); 

     connection.setAutoCommit(true); 


     resultSet = statement.executeQuery("SELECT assignmentID, deadline, lectureID FROM Assignment"); 
     metaData = resultSet.getMetaData(); 
     numberOfColumns = metaData.getColumnCount(); 
     System.out.println("assignment"); 
     can.displayTable(resultSet, numberOfColumns, metaData); 


     resultSet = statement.executeQuery("SELECT instructorID, instructorName FROM Instructor"); 
     metaData = resultSet.getMetaData(); 
     numberOfColumns = metaData.getColumnCount(); 
     System.out.println("instructor"); 
     can.displayTable(resultSet, numberOfColumns, metaData); 


     resultSet = statement.executeQuery("SELECT lectureID, lectureName, time, credit, instructorID FROM LectureStudent"); 
     metaData = resultSet.getMetaData(); 
     numberOfColumns = metaData.getColumnCount(); 
     System.out.println("lecture"); 
     can.displayTable(resultSet, numberOfColumns, metaData); 


     resultSet = statement.executeQuery("SELECT lectureID, studentID FROM LectureStudent"); 
     metaData = resultSet.getMetaData(); 
     numberOfColumns = metaData.getColumnCount(); 
     System.out.println("lecture_student"); 
     can.displayTable(resultSet, numberOfColumns, metaData); 


     resultSet = statement.executeQuery("SELECT resultID, grade FROM Result"); 
     metaData = resultSet.getMetaData(); 
     numberOfColumns = metaData.getColumnCount(); 
     System.out.println("result"); 
     can.displayTable(resultSet, numberOfColumns, metaData); 


     resultSet = statement.executeQuery("SELECT studentID, studentName FROM Student"); 
     metaData = resultSet.getMetaData(); 
     numberOfColumns = metaData.getColumnCount(); 
     System.out.println("student"); 
     can.displayTable(resultSet, numberOfColumns, metaData); 


    } catch (SQLException e) { 
     e.printStackTrace(); 
    } 
    finally { 
     // close the connection! 
     try { 
      if (connection != null) { 
       connection.close(); 
      } 
     } catch (SQLException e) {} 
    } 

}//END main 



public void displayTable(ResultSet resultSet, int numberOfColumns, ResultSetMetaData metaData) { 

    try { 
     for(int i=1; i<=numberOfColumns; i++) 
      System.out.printf("%-8s\t", metaData.getColumnName(i)); 
     System.out.println(); 

     while(resultSet.next()) { 

      for(int i=1 ; i<=numberOfColumns ; i++) 
       System.out.printf("%-8s\t", resultSet.getObject(i)); 
      System.out.println(); 

     } 
    } catch (Exception e) { } 



}//END displayTable 

}//END Can 

它在创建表格时工作正常。但问题是，当我运行该程序时，出现以下有关语法错误的奇怪错误。

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 '' at line 1 
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) 
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) 
at java.lang.reflect.Constructor.newInstance(Constructor.java:513) 
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) 
at com.mysql.jdbc.Util.getInstance(Util.java:386) 
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1052) 
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4096) 
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4028) 
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2490) 
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2651) 
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2677) 
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1748) 
at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1665) 
at Can.main(Can.java:35) 

任何想法？

谢谢，C @ N。

Answer 1

为什么你在你的ID字段中放入''...这是一个INT类型的列。让你的插入查询像

statement.executeUpdate("INSERT INTO Instructor VALUES(1, 'instructorName1')"); 

你上次创建语句缺少右括号)。

Answer 2

看看第35行的错误信息是怎么回事？如果这些行在粘贴它们时是正确的，那是最后一次创建Table语句？那里有什么错误的SQL。

更新：正如@ypercube对您的问题的评论所指出的那样：您在那里错过了一个右括号！

Answer 3

你缺少一个右括号在最后创建声明：... PRIMARY KEY (resultID)");

它应该是：

statement.executeUpdate("CREATE TABLE Results" + 
     "(resultID INT, grade FLOAT, PRIMARY KEY (resultID))"); 
                  ^
           parenthesis added here -----|