刪除哪些字段指定值

Question

我想刪除其中有場與由我指定的值記錄記錄：

public static void delete(String firstName, String lastName, int age) 
{ 
    try 
    { 
     Statement myStmt = connection.createStatement(); 
     String sql = "delete from students where firstName='" + firstName + "', lastName='" + lastName + "', age='" + age + "'"; 
     myStmt.executeUpdate(sql); 
    } 
    catch (SQLException e) 
    {e.printStackTrace();} 
} 

的代碼不能正常工作。我絕對相信它的問題。請幫助我做正確的sql。我如何在表格中找到哪些字段由我指定的值？

這裏是一個錯誤，我越來越：

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 'where firstName='deleted', lastName='deleted', age='10'' at line 1 
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) 
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) 
    at java.lang.reflect.Constructor.newInstance(Unknown Source) 
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:425) 
    at com.mysql.jdbc.Util.getInstance(Util.java:408) 
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:943) 
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3973) 
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3909) 
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2527) 
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2680) 
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2486) 
    at com.mysql.jdbc.StatementImpl.executeUpdateInternal(StatementImpl.java:1552) 
    at com.mysql.jdbc.StatementImpl.executeLargeUpdate(StatementImpl.java:2607) 
    at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1480) 
    at Driver.delete(Driver.java:76) 
    at Driver.main(Driver.java:18) 

Answer 1

爲了避免所有你必須在使用PreparedStatement這個語法錯誤，甚至SQL注入，因此，你可以使用：

String query = "delete from students where firstName=? and lastName=? and age=?"; 
try (PreparedStatement delete = connection.prepareStatement(query)) { 

    delete.setString(1, firstName); 
    delete.setString(2, lastName); 
    delete.setInt(3, age);//<-----------(1) 

    delete.executeUpdate(); 
} 

• （1）我不知道如果年齡爲int或varchar，所以如果年齡是一個字符串，你必須改用setString。

---

你真正的問題是，你必須使用and，or在where而不是,

where firstName='" + firstName + "', lastName='" + lastName + "', age='" + age + "'"; 
//----------------------------------^----------------------------^ 

Answer 2

你的SQL不正確，應該是：

String sql = "DELETE FROM students WHERE firstName='" + firstName + "' AND lastName='" + lastName + "' AND age='" + age + "'"; 

你可以在你WHERE子句只獨立的條件下使用的關鍵字，如AND或OR逗號在SQL查詢的該部分中是無效的分隔符。