我正在使用以下代码通过 Java 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
在创建表格时它工作正常。但问题是我在运行程序时收到以下关于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)
有任何想法吗?
谢谢,C@N。