我想使用WITH语句“声明”有效的多个临时表。我尝试执行的查询是这样的:
WITH table_1 AS (
SELECT GENERATE_SERIES('2012-06-29', '2012-07-03', '1 day'::INTERVAL) AS date
)
WITH table_2 AS (
SELECT GENERATE_SERIES('2012-06-30', '2012-07-13', '1 day'::INTERVAL) AS date
)
SELECT * FROM table_1
WHERE date IN table_2
我已经阅读了PostgreSQL documentation,并研究了如何使用多个WITH
语句,但无法找到答案。
发布于 2016-07-01 12:24:30
根据其他注释,第二个公用表表达式CTE的前面是逗号,而不是WITH语句,因此
WITH cte1 AS (SELECT...)
, cte2 AS (SELECT...)
SELECT *
FROM
cte1 c1
INNER JOIN cte2 c2
ON ........
就您的实际查询而言,此语法应该适用于PostgreSql、Oracle和sql-server,而后者通常会以分号(;WTIH
)继续WITH
,但这是因为通常sql-server人员(包括我自己)不会结束之前需要在定义CTE之前结束的语句...
但是请注意,与WHERE
语句相关的还有第二个语法问题。WHERE date IN table_2
无效,因为您从未实际引用过table_2中的值/列。我更喜欢INNER JOIN
而不是IN
或Exists
,因此以下语法适用于JOIN
WITH table_1 AS (
SELECT GENERATE_SERIES('2012-06-29', '2012-07-03', '1 day'::INTERVAL) AS date
)
, table_2 AS (
SELECT GENERATE_SERIES('2012-06-30', '2012-07-13', '1 day'::INTERVAL) AS date
)
SELECT *
FROM
table_1 t1
INNER JOIN
table_2 t2
ON t1.date = t2.date
;
如果您想保持它通常存在的方式,它将比IN更好,但是要使用IN,您需要在where中使用实际的SELECT语句。
SELECT *
FROM
table_1 t1
WHERE t1.date IN (SELECT date FROM table_2);
当date
可能是NULL
时,IN是非常有问题的,所以如果你不想使用JOIN
,那么我建议使用EXISTS
。如下所示:
SELECT *
FROM
table_1 t1
WHERE EXISTS (SELECT * FROM table_2 t2 WHERE t2.date = t1.date);
发布于 2020-05-20 18:21:03
您还可以使用WITH语句链接您的结果。例如:
WITH tab1 as (Your SQL statement),
tab2 as ( SELECT ... FROM tab1 WHERE your filter),
tab3 as ( SELECT ... FROM tab2 WHERE your filter)
SELECT * FROM tab3;
https://stackoverflow.com/questions/38136854
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