如何使用SQL查询中DBTABLE定义表? [英] How to use SQL query to define table in dbtable?
问题描述
在 JDBC到其他数据库,我发现 DBTABLE
参数如下解释:
In JDBC To Other Databases I found the following explanation of dbtable
parameter:
这应该读的JDBC表。请注意,任何有效的从SQL查询的WHERE子句可以使用。例如,而不是一个完整的表,你也可以在括号中使用子查询。
The JDBC table that should be read. Note that anything that is valid in a FROM clause of a SQL query can be used. For example, instead of a full table you could also use a subquery in parentheses.
当我使用code:
CREATE TEMPORARY TABLE jdbcTable
USING org.apache.spark.sql.jdbc
OPTIONS (
url "jdbc:postgresql:dbserver",
dbtable "mytable"
)
一切都很正常,但以下内容:
everything works great, but the following:
dbtable "SELECT * FROM mytable"
导致错误:
什么是错的?
推荐答案
由于 DBTABLE
被用作 SELECT $ C源$ C>声明它已成为这将是适用于普通的SQL查询的窗体。如果你想使用子查询你应该通过括号中的查询,并提供了一个别名:
Since dbtable
is used as a source for the SELECT
statement it has be in a form which would be valid for normal SQL query. If you want to use subquery you should pass a query in parentheses and provide an alias:
CREATE TEMPORARY TABLE jdbcTable
USING org.apache.spark.sql.jdbc
OPTIONS (
url "jdbc:postgresql:dbserver",
dbtable "(SELECT * FROM mytable) tmp"
);
有将被传递到数据库:
SELECT * FROM (SELECT * FROM mytable) tmp WHERE 1=0
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