本文介绍了JAVA,SQL,插入无重复项的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我试图插入没有重复的表中.我在Java中使用SQL derbyclient
.该代码不起作用('where not exists'
错误).有什么主意吗?
I am trying to insert into a table without duplicates. I am using SQL derbyclient
in Java. The code is not working (error with 'where not exists'
). Any idea?
Connection connection = DriverManager.getConnection("jdbc:derby://localhost:1527/PetroleumDataStorageSystemDB;create=true");
PreparedStatement statement;
int i = 1;
int progress = 0;
for (Refuel refuelList1 : refuelList) {
progress = (i / refuelList.size()) * 100;
String sql = "INSERT INTO refuel (id_tank, time, fuel_volume, "
+ "refueling_speed) VALUES (?,?,?,?) "
+ "WHERE NOT EXISTS (SELECT * FROM refuel WHERE "
+ "id_tank = ? AND time = ? AND fuel_volume = ? AND "
+ "refueling_speed = ?)";
statement = connection.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
statement.setInt(1, refuelList1.getTankID());
statement.setString(2, refuelList1.getTime());
statement.setDouble(3, refuelList1.getFuelVolume());
statement.setDouble(4, refuelList1.getRefuelingSpeed());
statement.execute();
i++;
}
推荐答案
问题是如何构建查询.那不是有效的INSERT
语法
The problem is how you build your query. That isnt a valid INSERT
syntaxis
首先在您的数据库上尝试使用类似的方法使用伪值.
Try something like this on your db first with dummy values.
INSERT INTO refuel (id_tank, time, fuel_volume, refueling_speed)
SELECT ?, ?, ?, ?
FROM refuel
WHERE NOT EXISTS (SELECT
FROM refuel
WHERE
id_tank = ?
AND time = ?
AND fuel_volume = ?
AND refueling_speed = ?);
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