如何在C#中使用访问数据库连接表和查询

Question

这是我如何加入2个表并选择它:

OleDbDataAdapter DataA = new OleDbDataAdapter(@"Select tfr.FeedID, tf.FeedName, tfr.FeedQuantity, tf.DM
                                                        FROM tFeeds AS tf
                                                        INNER JOIN tFeedsRations AS tfr ON (tf.FeedID=tfr.FeedID)", Connection);

但是如何为这个select命令添加访问查询呢？例如,我想将此语句添加到我的select命令:

Select qfq.FeedDMQuantites
From qFeeds_Quantities as qfq

我该怎么办？

Answer 1

好吧JOIN,为此表添加另一个条件qFeeds_Quantities(假设您与此表或其他表中的公共列有关系).

假设你有一个像FeedID这个新表一样的公共列,你可以做另一个JOIN像

select tfr.FeedID, tf.FeedName, tfr.FeedQuantity, 
tf.DM, qfq.FeedDMQuantites
FROM (tFeeds AS tf
INNER JOIN tFeedsRations AS tfr ON tf.FeedID = tfr.FeedID)
INNER JOIN qFeeds_Quantities as qfq ON tf.FeedID = qfq.FeedID;

如果你想包含另一个,JOIN那么括号如

FROM ((tFeeds AS tf
INNER JOIN tFeedsRations AS tfr ON tf.FeedID = tfr.FeedID)
INNER JOIN qFeeds_Quantities as qfq ON tf.FeedID = qfq.FeedID)
INNER JOIN BLAH AS bll ON bll.test = tf.test;