Question

我正在尝试帮助同事在两个oracle表上进行内部联接，以便他可以在报表上构建特定的图表。

我没有Oracle经验，只有SQL Server并且已经得到了合适的声明，但是没有用。

SELECT concat(concat(month("a.timestamp"),','),day("a.timestamp")) as monthDay
    , min("a.data_value") as minTemp
    , max("a.data_value") as maxTemp
    , "b.forecast" as forecastTemp
    , "a.timestamp" as date
FROM table1 a
WHERE "a.category" = 'temperature'
GROUP BY concat(concat(month("timestamp"),','),day("timestamp"))
INNER JOIN (SELECT "forecast"
           , "timestamp"
        FROM table2
        WHERE "category" = 'temperature') b
ON "a.timestamp" = "b.timestamp"

出于某种原因，它不喜欢我的别名。由于某种原因，它不喜欢没有引号。

当我使用完全得分的名字时，它仍然失败，因为：

ORA-00933 SQL command not properly ended

Answer 1

查询的顺序应为

SELECT
FROM
INNER JOIN
WHERE
GROUP BY

如下

SELECT concat(concat(month("a.timestamp"),','),day("a.timestamp")) as monthDay
    , min("a.data_value") as minTemp
    , max("a.data_value") as maxTemp
    , "b.forecast" as forecastTemp
    , "a.timestamp" as date
FROM table1 a
INNER JOIN (SELECT "forecast"
       , "timestamp"
      FROM table2
      WHERE "category" = 'temperature') b
ON "a.timestamp" = "b.timestamp"
WHERE "category" = 'temperature'
GROUP BY concat(concat(month("timestamp"),','),day("timestamp"))

Answer 2

在大量的尝试中，这是另一个尝试。

table2可以移出子查询;在类别上加入table1以及
请注意，所有非聚合列（来自SELECT）都必须包含在GROUP BY子句中。似乎a.timestamp包含的信息不仅仅是月和日 - 如果是这样的话，它可能会破坏整个结果集，因为数据不会按 monthday <分组/ em>，但是整个日期 - 如果有必要，请考虑将其从SELECT中删除

SELECT TO_CHAR(a.timestamp,'mm.dd') monthday, MIN(a.data_value) mintemp, MAX(a.data_value) maxtemp, b.forecast forecasttemp, a.timestamp c_date FROM table1 a JOIN table2 b ON a.timestamp = b.timestamp AND a.category = b.category WHERE a.category = 'temperature' GROUP BY TO_CHAR(a.timestamp,'mm.dd'), b.forecast, a.timestamp;

Answer 3

select的正确（简化）语法是

SELECT <columns>
FROM table1 <alias>
   JOIN table2 <alias> <join_condition>
WHERE <condition>
GROUP BY <group by columns>

Answer 4

你做错了。使用子查询：

SELECT c.*,  b.`forecast` as forecastTemp
FROM
(SELECT concat(concat(month(a.`timestamp`),','),day(a.`timestamp`)) as monthDay
    , min(a.`data_value`) as minTemp
    , max(a.`data_value`) as maxTemp
    , a.`timestamp` as date
FROM table1 a
WHERE `category`='temperature'
GROUP BY concat(concat(month(`timestamp`),','),day(`timestamp`))) c
INNER JOIN (SELECT `forecast`
           , `timestamp`
        FROM table2
        WHERE `category` = 'temperature') b
ON c.`timestamp` = b.`timestamp`;

Answer 5

查询应如下所示：

SELECT to_char(a.timestamp, 'MM-DD') as monthDay,
       min(a.data_value) as minTemp,
       max(a.data_value) as maxTemp,
       b.forecast as forecastTemp
FROM table1 a JOIN
     table2 b
     ON a.timestamp = b.timestamp and b.category = 'temperature'
WHERE a.category = 'temperature'
GROUP BY to_char(timestamp, 'MM-DD'), b.forecast;

我不是100％确定这是你想要的。您的查询有很多问题和复杂性：

FROM子句中不需要子查询。
您可以使用to_char()代替更复杂的日期字符串处理。
group by未包含所有相关字段。
不要使用双引号，除非确实需要。

Answer 6

除了其他答案提到的组件的顺序（where等于join之后），您还需要删除所有双引号字符。在Oracle中，这些覆盖了标准命名规则，因此"a.category"仅在您的表实际上有一个名为"a.category"的列，例如

时才有效。

create table demo ("a.category" varchar2(10));

insert into demo ("a.category") values ('Weird');

select d."a.category" from demo d;

很少需要这样做。

如何在Oracle表中进行连接？

6 个答案: