删除sql不删除

我正试图从我的表中删除一个事件。 但是我似乎无法让它发挥作用。 我的SQL语句是：

public void deleteEvent(String eventName){ String query = "DELETE FROM `Event` WHERE `eventName` ='"+eventName+"' LIMIT 1"; db.update(query); System.out.println (query); } 

使用MySQL db

Answer 1

尝试使用以下内容：

 String query = "DELETE FROM `Event` WHERE `eventName` ='"+eventName+"' LIMIT 1"; try { Connection con = getConnection(); Statement s = con.createStatement(); s.execute(query); } catch (Exception ex) { ex.printStackTrace(); } 

您必须编写getConnection()方法的代码以返回有效的数据库连接。

Answer 2

我建议使用Statement.executeUpdate方法，因为它返回一个整数。 因此，在执行此删除查询后，如果您确实删除了任何记录，您也将获得信息（在这种情况下，您希望此方法返回1，因为您使用的是LIMIT = 1）。 我建议你在不需要时立即关闭Statement，这里是骨架实现：

 private void performDelete(Connection conn, String deleteQuery, int expectedResult) throws SQLException { Statement stmt = conn.createStatement(); int result = -1; try { result = stmt.executeUpdate(deleteQuery); if(result != expectedResult) { //Here you can check the result. Perhaps you don't need this part throw new IllegalStateException("Develete query did not return expected value"); } } catch(SQLException e) { //Good practice if you use loggers - log it here and rethrow upper. //Or perhaps you don't need to bother in upper layer if the operation //was successful or not - in such case, just log it and thats it. throw e; } finally { //This should be always used in conjunction with ReultSets. //It is not 100% necessary here, but it will not hurt stmt.close(); } }