hadoop - 插入覆盖目录的 Hive Case 语句

Question

当尝试使用以下逻辑运行 HQL 脚本时，我收到错误:

ParseException line 4:0 cannot recognize input near 'CASE' 'WHEN' 'mytable' in serde properties specification 

脚本逻辑

INSERT OVERWRITE DIRECTORY '/example/path'
ROW FORMAT DELIMITED
FIELDS TERMINATED BY ','
CASE WHEN ${hiveconf:tbl_name}='mytable'
THEN SELECT * FROM ${hiveconf:tbl_name} LEFT OUTER JOIN ...;
WHEN ${hiveconf:tbl_name}='mytable2'
THEN SELECT * FROM ${hiveconf:tbl_name} LEFT OUTER JOIN ...;
ELSE THEN
END

我如何根据传入的 tbl_name 参数的值正确地为 INSERT OVERWRITE DIRECTORY 分配一个选择语句？

更新 1:修改为:

SELECT CASE WHEN ${hiveconf:tbl_name}='mytable'
THEN * FROM WHEN ${hiveconf:tbl_name}='mytable'
WHEN ${hiveconf:tbl_name}='mytable2'
THEN * FROM ${hiveconf:tbl_name} LEFT OUTER JOIN ...;
ELSE THEN
END

它的错误是:

FAILED: ParseException line 9:9 cannot recognize input near '*' 'FROM' 'mytable' in expression specification

更新 2:当修改为:

SELECT * CASE WHEN ${hiveconf:tbl_name}='mytable'
THEN FROM WHEN ${hiveconf:tbl_name}='mytable'
WHEN ${hiveconf:tbl_name}='mytable2'
THEN FROM ${hiveconf:tbl_name} LEFT OUTER JOIN ...;
ELSE THEN
END

它的错误是:

FAILED: ParseException line 8:9 Failed to recognize predicate 'CASE'. Failed rule: 'regularBody' in statement

Answer 1

快速解决方案是使用 UNION ALL+WHERE。像这样:

insert overwrite directory
...
select * from mytable where '${hiveconf:tbl_name}'='mytable'
union all
select * from mytable2 where '${hiveconf:tbl_name}'='mytable2'

将您的联接添加到每个选择。