Java jdbc只批量插入新行

Question

如何仅对新行（目标表中不存在ID列值）使用jdbc有效地执行对Sql Server表的批处理插入？

实际上，我使用PreparedStatement对象创建批处理，但没有“仅在新行时插入”逻辑：

String sqlInsertStub = "INSERT INTO mytable (id, col2, col3) values (?, ?, ?)";

try (PreparedStatement preparedStatement = connection.prepareStatement(sqlInsertStub)) {

    connection.setAutoCommit(false);

    int processed = 0;

    while (resultSet.next()) {

        // [...]

        preparedStatement.setInt(1, id);
        preparedStatement.setString(2, col2);
        preparedStatement.setString(3, col3);

        preparedStatement.addBatch();

        if (++processed % BATCH_SIZE == 0) {
            preparedStatement.executeBatch();
            connection.commit();
        }

    }

    preparedStatement.executeBatch();
    connection.commit();    


catch (Exception e) {

    connection.rollBack();
    e.printStackTrace();
    System.exit(1);

}

Answer 1

我还发现了使用merge的另一种可能的解决方案：

String sqlInsertStub = "MERGE INTO mytable a USING (SELECT ? ID) b " +
                        "ON (a.ID = b.ID)" +
                        "WHEN NOT MATCHED " +
                        "THEN INSERT (ID, COL1, COL2) VALUES(b.ID, ?, ?)";

Answer 2

一个选项是在表中决定唯一性的三列上添加唯一约束。然后，尝试插入重复记录会导致Java异常。但是，这可能会导致整个批次失败。如果需要其他选项，可以将查询更改为以下内容：

INSERT INTO mytable
SELECT ?, ?, ?
WHERE NOT EXISTS (SELECT 1 FROM mytable
                  WHERE id = ? AND col2 = ? AND col3 = ?);

对此查询，您将值绑定两次，如下所示：

preparedStatement.setInt(1, id);
preparedStatement.setString(2, col2);
preparedStatement.setString(3, col3);
preparedStatement.setInt(4, id);
preparedStatement.setString(5, col2);
preparedStatement.setString(6, col3);