JDBC驱动程序不支持批量更新并检索标识列.为什么？

Question

我的问题是我想做JDBC批量插入和检索标识列值.MS SQL驱动程序不支持此功能.有人可以指导我,如何解决这个问题？

Answer 1

如前面提到的问题在这里,.getGeneratedKeys根本不工作后.executeBatch的SQL Server.我刚刚确认使用最新版本的情况仍然如此

• SQL Server JDBC驱动程序(4.1预览版)和
• jTDS(1.3.1)

因此,您似乎只需要单独执行插入操作,而无需批处理.也就是说,而不是像这样的代码

String[] stringsToInsert = new String[] { "foo", "bar", "baz" };
try (PreparedStatement ps = conn.prepareStatement(
        "INSERT INTO junk (textcol) VALUES (?)", 
        PreparedStatement.RETURN_GENERATED_KEYS)) {
    for (String s : stringsToInsert) {
        ps.setString(1, s);
        ps.addBatch();
    }
    ps.executeBatch();
    try (ResultSet rs = ps.getGeneratedKeys()) {
        while (rs.next()) {
            System.out.println(rs.getInt(1));
        }
    }
}

你需要使用这样的代码

String[] stringsToInsert = new String[] { "foo", "bar", "baz" };
try (PreparedStatement ps = conn.prepareStatement(
        "INSERT INTO junk (textcol) VALUES (?)", 
        PreparedStatement.RETURN_GENERATED_KEYS)) {
    for (String s : stringsToInsert) {
        ps.setString(1, s);
        if (ps.executeUpdate() > 0) {
            try (ResultSet rs = ps.getGeneratedKeys()) {
                rs.next();
                System.out.println(rs.getInt(1));
            }
        }
    }
}

请注意,您仍然可以.setAutoCommit(false)在事务中使用和执行插入操作,而不是批量操作.

至于为什么不支持该操作,这里提出的jTDS功能请求是在九(9)年前提交的,其中一个响应是

在确定是否值得付出努力之前,我将不得不看一看如何在jTDS中实现这样的功能.

由于jTDS和SQL Server JDBC驱动程序都没有实现它(至少现在还没有;它是微软JDBC驱动程序的雷达),也许对该功能的需求不足.

附录

作为一种解决方法,我认为这可行

String[] stringsToInsert = new String[] { "foo", "bar", "baz" };
try (Statement s = conn.createStatement()) {
    s.executeUpdate(
            "CREATE TABLE #StuffToInsert (" +
                "id INT IDENTITY(1,1) PRIMARY KEY, " +
                "textcol NVARCHAR(100)" +
            ")");
}
try (PreparedStatement ps = conn.prepareStatement(
        "INSERT INTO #StuffToInsert (textcol) VALUES (?)")) {
    for (String s : stringsToInsert) {
        ps.setString(1, s);
        ps.addBatch();
    }
    ps.executeBatch();
}
try (PreparedStatement ps = conn.prepareStatement(
        "INSERT INTO junk (textcol) SELECT textcol FROM #StuffToInsert", 
        Statement.RETURN_GENERATED_KEYS)) {
    ps.executeUpdate();
    try (ResultSet rs = ps.getGeneratedKeys()) {
        while (rs.next()) {
            System.out.println(rs.getInt(1));
        }
    }
}

但不幸的是,.getGeneratedKeys只返回插入的最后一行的单个生成密钥.

如果通过网络连接发送大量单个(未批处理)插入将是一个问题,那么此解决方法可能会有所帮助:

String[] stringsToInsert = new String[] { "foo", "bar", "baz" };
try (Statement s = conn.createStatement()) {
    s.executeUpdate(
            "CREATE TABLE #StuffToInsert (" +
                "id INT IDENTITY(1,1) PRIMARY KEY, " +
                "textcol NVARCHAR(100)" +
            ")");
}
try (PreparedStatement ps = conn.prepareStatement(
        "INSERT INTO #StuffToInsert (textcol) VALUES (?)")) {
    for (String s : stringsToInsert) {
        ps.setString(1, s);
        ps.addBatch();
    }
    ps.executeBatch();
}
try (PreparedStatement ps = conn.prepareStatement(
        "SET NOCOUNT ON; " +
        "DECLARE @GeneratedKeys TABLE(id INT IDENTITY(1,1) PRIMARY KEY, newkey INT); " +
        "DECLARE @text NVARCHAR(100); " +
        "DECLARE crsr CURSOR FOR " +
        "   SELECT textcol FROM #StuffToInsert ORDER BY id; " +
        "OPEN crsr; " +
        "FETCH NEXT FROM crsr INTO @text; " +
        "WHILE @@FETCH_STATUS = 0 " +
        "BEGIN " +
        "   INSERT INTO junk (textcol) VALUES (@text); " +
        "   INSERT INTO @GeneratedKeys (newkey) SELECT @@IDENTITY; " +
        "   FETCH NEXT FROM crsr INTO @text; " +
        "END " +
        "CLOSE crsr; " +
        "DEALLOCATE crsr; " +
        "SELECT newkey FROM @GeneratedKeys ORDER BY id; ")) {
    try (ResultSet rs = ps.executeQuery()) {
        while (rs.next()) {
            System.out.println(rs.getInt(1));
        }
    }
}

但是这种方法不尊重Java代码中的AutoCommit设置,因此无法进行回滚.