Question

我正在多个JOIN表上执行查询：

SELECT  TableA.*,
        TableB.Data             as Data_B,
        TableC.Data             as Data_C,
        TableD.Data             as Data_D,
        TableE.*
FROM TableA     JOIN TableB         ON TableB.ID = TableA.ID
                JOIN TableC         ON TableC.ID = TableB.ID
                JOIN TableD         ON TableD.ID = TableC.ID
                JOIN TableE         ON TableE.ID = TableA.ID
WHERE DataToFind = '$SubmittedData'

它运行良好，但由于TableA是主表，而TableE是一个通过密钥ID与TableA关联的多子表，当我在TableA字段上执行搜索时，我得到TableA的多个行，与TableE记录一样多。 / p>

由于我只是在我执行搜索后想要DISTINCT，我的理想查询应该是：

SELECT DISTINCT ID FROM
(
SELECT  TableA.*,
        TableB.Data             as Data_B,
        TableC.Data             as Data_C,
        TableD.Data             as Data_D,
        TableE.*
FROM TableA     JOIN TableB         ON TableB.ID = TableA.ID
                JOIN TableC         ON TableC.ID = TableB.ID
                JOIN TableD         ON TableD.ID = TableC.ID
                JOIN TableE         ON TableE.ID = TableA.ID
WHERE DataToFind = '$SubmittedData'
)
WHERE ID IS NOT NULL

但由于我收到“意外令牌”和其他语法错误，因此无效。

你能帮我找一下如何正确格式化吗？

P.S。我不在乎是否丢失了一些TableE记录，因为我可以在需要时使用找到的ID恢复它们。

Answer 1

如果你想要不同的id，那么把它们全部放在一个select语句中：

SELECT DISTINCT TableA.ID
FROM TableA JOIN
     TableB
     ON TableB.ID = TableA.ID JOIN
     TableC
     ON TableC.ID = TableB.ID JOIN
     TableD
     ON TableD.ID = TableC.ID JOIN
     TableE
     ON TableE.ID = TableA.ID
WHERE DataToFind = '$SubmittedData';

您的版本存在问题，因为子查询中有两列名为ID。这将产生另一个错误。

Answer 2

您的查询没问题。它只是缺少子查询的表别名，如

SELECT DISTINCT ID FROM
(
    SELECT  tableA.*,
            TableB.Data             as Data_B,
            TableC.Data             as Data_C,
            TableD.Data             as Data_D
            TableE.*
    FROM tableA     JOIN tableB         ON tableB.ID = tableA.ID
                    JOIN tableC         ON tableC.ID = tableB.ID
                    JOIN tableD         ON tableD.ID = tableC.ID
                    JOIN tableE         ON tableE.ID = tableA.ID
    WHERE DataToFound = '$SubmittedData'
) xxx            <-- missing
WHERE ProcedureID IS NOT NULL

MySQL - 查询后删除冗余字段

2 个答案: