Question

我在我的java应用程序中使用SQLite，我在我的数据库中创建了一些表。当我将元素插入人员表(ID INTEGER PRIMARY KEY AUTOINCREMENT,NAME CHAR(50) NOT NULL UNIQUE)时，我在下面得到了例外：

java.sql.SQLException: [SQLITE_CONSTRAINT] Abort due to constraint violation (column NAME is not unique) at org.sqlite.DB.newSQLException(DB.java:383) at org.sqlite.DB.newSQLException(DB.java:387) at org.sqlite.DB.execute(DB.java:342) at org.sqlite.DB.executeUpdate(DB.java:363) at org.sqlite.PrepStmt.executeUpdate(PrepStmt.java:85) at epfl.lca1.spism.DesktopClient$1.run(Myclass.java:71) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:705) at java.awt.EventQueue.access$000(EventQueue.java:101) at java.awt.EventQueue$3.run(EventQueue.java:666) at java.awt.EventQueue$3.run(EventQueue.java:664) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76) at java.awt.EventQueue.dispatchEvent(EventQueue.java:675) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105) at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

我的代码是：

final PreparedStatement s;
    Connection db = openOrCreateDatabase();
    try {
        s = db.prepareStatement("INSERT INTO People"+
                                "(Name) VALUES"+ 
                                "(?)");
    SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            System.out.printf("A: %d\n", Thread.currentThread().getId());

            for (People p : Peoplearray) {
                try {
                    s.setString(1,p.toString());
                    s.executeUpdate(); // line 71
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    });
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

也许有些元素插入两次，我怎么能忽略插入已存在的元素？

Answer 1

SQLite的INSERT可以与冲突解决子句一起使用，以指定在发生约束违规时会发生什么。这将忽略任何插入重复值的尝试：

INSERT OR IGNORE INTO People (Name) VALUES (?)

Answer 2

由于您的Name列为unique，因此两个条目/行的名称值不能相同。因此，将您的查询更改为

INSERT INTO People(Name)
Select ? from dual
WHERE NOT EXISTS
   (SELECT *
    FROM People
    WHERE Name= ?)

仅当不存在具有相同名称的条目时，才会插入条目。

只是为了清除混淆DUAL是大多数数据库中的特殊表。您可以阅读其Wiki。

java.sql.SQLException：[SQLITE_CONSTRAINT]

2 个答案: