mysql - sql select 多次返回同一组行

Question

我正在处理查询，它多次显示相同的行，只是在两次之间交替。我测试了从所有提到的表中选择每一列，但没有看到行之间的差异。请注意，应该只返回两行，而我得到了超过 10 行。

我认为这与连接 mlc 表和 trv 表有关，但我不知道如何修复它。任何帮助表示赞赏。谢谢。

SELECT mlc.click_amount AS memPayout
        FROM tbl_trackvalue AS trv, tbl_tracking AS t, tbl_offers AS off, tblusers AS usr, tbl_mailchimp_trackvalue as mlc
        WHERE mlc.tracking_id = trv.tracking_id
              AND off.id = t.offer_id
              AND off.offer_type = 'mailchimp'
              AND usr.id = trv.tr_user_id
              AND trv.tr_user_id =1454
              AND mlc.requested_date = '2014-01-21'
              AND mlc.payment_status = 'pending'
              AND mlc.requested_status = 'declined'

更新的代码:

SELECT mlc.click_amount AS memPayout
                                        FROM tbl_trackvalue AS trv, tbl_offers AS off, tbl_mailchimp_trackvalue as mlc
                                        WHERE mlc.tracking_id = trv.tracking_id
                                        AND off.id = trv.tr_offer_id
                                        AND off.offer_type = 'mailchimp'
                                        AND trv.tr_user_id =1454
                                        AND mlc.requested_date = '2014-01-21'
                                        AND mlc.payment_status = 'pending'
                                        AND mlc.requested_status = 'declined'

更新 II(再次更改，这次有效。感谢您的帮助。我很新，现在意识到明确命名连接的重要性:

SELECT mlc.click_amount AS memPayout
    FROM  tbl_mailchimp_trackvalue as mlc inner join tbl_trackvalue AS trv on mlc.tracking_id=trv.tracking_id
    WHERE trv.type = 'mailchimp'
    AND trv.tr_user_id =1454
    AND mlc.requested_date = '2014-01-21'
    AND mlc.payment_status = 'pending'
    AND mlc.requested_status = 'declined'

Answer 1

您在 off 上加入 t，在 usr 和 mlc 上加入 trv >，但是这两个连接 block 之间永远不会有任何连接。