在 Google BigQuery(使用#standardSQL)上,当 2 个表之间存在连接时,我需要对每个表的所有列应用固定前缀。
这是场景,我有这样的结构:
#standardSQL
WITH user AS (
SELECT "john" as name, "smith" as surname, 1 as parent
UNION ALL
SELECT "maggie" as name, "smith" as surname, 2 as parent
),
parent AS (
SELECT 1 as id, "john" as name, "doe" as surname
UNION ALL
SELECT 2 as id, "jane" as name, "smith" as surname
)
用户表
+-----+--------+---------+--------+
| Row | name | surname | parent |
+-----+--------+---------+--------+
| 1 | john | smith | 1 |
| 2 | maggie | smith | 2 |
+-----+--------+---------+--------+
父表
+-----+----+------+---------+
| Row | id | name | surname |
+-----+----+------+---------+
| 1 | 1 | john | doe |
| 2 | 2 | jane | smith |
+-----+----+------+---------+
像这样的查询
SELECT u.*, p.* FROM user u JOIN parent p ON u.parent = p.id
产生以下错误
Error: Duplicate column names in the result are not supported. Found duplicate(s): name, surname
我想避免像这样对表执行自定义别名
SELECT
u.name as user_name,
u.surname as user_surname,
p.name as parent_name,
p.surname as parent_surname
FROM user u JOIN parent p ON u.parent = p.id
+-----+-----------+--------------+-------------+----------------+
| Row | user_name | user_surname | parent_name | parent_surname |
+-----+-----------+--------------+-------------+----------------+
| 1 | john | smith | john | doe |
| 2 | maggie | smith | jane | smith |
+-----+-----------+--------------+-------------+----------------+
如果表格将更改字段,我需要每次编辑语句(或语句)以应用具有给定前缀的新字段。所以这种使用固定列名的方法不是合适的方法
有没有一种方法,一个查询运算符,为了获得上面提到的表,自动应用前缀?就像是:
SELECT u.* AS user_*, p.* AS parent_*
FROM user u JOIN parent p ON u.parent = p.id