Question

我有3个表（up_1，up_2，up_3）。它们都具有相同的数据库结构（id，value，date，time）。我需要在特定日期列出它们。

例如，如果我选择2015年11月17日，它将在2015年11月17日列出所有数据。

以下是数据集的示例

ucp_1

----------------------------
id, value, date, time
----------------------------
1, 2, 17/11/2015, 09:00
2, 2, 17/11/2015, 10:00

ucp_2

----------------------------
id, value, date, time
----------------------------
1, 2, 17/11/2015, 11:00
2, 2, 17/11/2015, 12:00

ucp_3

----------------------------
id, value, date, time
----------------------------
1, 2, 17/11/2015, 13:00
2, 2, 17/11/2015, 14:00

我想要显示的结果

结果

-------------------------------------------------
value_ucp1, value_ucp2, value_ucp3, date, time
-------------------------------------------------
2, NULL, NULL, 17/11/2015, 09:00
2, NULL, NULL, 17/11/2015, 10:00
NULL, 2, NULL, 17/11/2015, 11:00
NULL, 2, NULL, 17/11/2015, 12:00
NULL, NULL, 2, 17/11/2015, 13:00
NULL, NULL, 2, 17/11/2015, 14:00

是否可以通过SQL Query实现这些结果？

Answer 1

您可以使用UNION ALL all来组合不同的表格。

   SELECT value AS ucp_1_Value,
           NULL AS ucp_2_Value,
           NULL AS ucp_3_Value,
           `date`,
            `time`
    FROM ucp_1 
    WHERE `date` = '17-11-2015'
        UNION ALL
    SELECT NULL AS ucp_1_Value,
          value AS ucp_2_Value,
          NULL AS ucp_3_Value,
         `date`,
          `time`
    FROM ucp_2 
    WHERE `date` = '17-11-2015'
        UNION ALL
    SELECT NULL AS ucp_1_Value ,
           NULL AS ucp_2_Value,
           value AS ucp_3_Value,
           `date`,
           `time` 
    FROM ucp_3 WHERE `date` = '17-11-2015'

希望这有帮助。

Answer 2

尝试将结果与UNION ALL合并为子查询，如此

SELECT
    merged.*
FROM (
    SELECT
        value AS value_ucp_1,
        NULL AS value_ucp_2,
        NULL AS value_ucp_3,
        date,
        time
    FROM up_1
    UNION ALL SELECT
        NULL,
        value,
        NULL,
        date,
        time
    FROM up_2
    UNION ALL SELECT
        NULL,
        NULL,
        value,
        date,
        time
    FROM up_3) AS merged
WHERE merged.date = '17-11-2015'

Answer 3

只是另一种观点。

<强>查询

select  case when t.ucp_id = 'ucp_1' then  t.value_ucp end as value_ucp1,
        case when t.ucp_id = 'ucp_2' then  t.value_ucp end as value_ucp2,
        case when t.ucp_id = 'ucp_3' then  t.value_ucp end as value_ucp3,
        t.`date`,t.`time`
from
(
    select 'ucp_1' as ucp_id,value as value_ucp,`date`,`time` from ucp_1 
    union all 
    select 'ucp_2' as ucp_id,value as value_ucp,`date`,`time` from ucp_2 
    union all 
    select 'ucp_3' as ucp_id,value as value_ucp,`date`,`time` from ucp_3
)t;

SQL Fiddle

Answer 4

重新组织数据库结构。使用您提到的结构创建一个表：

Table VDT
id_VDT, value, date, time

与其他字段链接到第一个字段的树表：

Table_A
id_VDT, {first table fields}

Table_B
id_VDT, {second table fields}

Table_C
id_VDT, {third table fields}

然后运行查询：

SELECT * FROM VDT, Table_A A, Table_B B, Table_C C
WHERE VDT.Date = {your date} AND 
      VDT.id_VDT=A.id_VDT AND VDT.id_VDT=B.id_VDT AND VDT.id_VDT=C.id_VDT
ORDER BY {your need}

通过组合3个表来列出数据

4 个答案: