在 teradata 中仅使用选择查询来迭代数组

Question

我正在尝试使用输入表来实现输出表。输入表包含 id 和 name，其中 id 包含数值，name 包含 JSON 值。我可以通过使用 'LOOP'、'Cursor' 等编写过程查询来获得输出。但是我们如何在 Teradata 中使用 select 查询语句来实现这一点。

输入表

S.No	Name
1	{ "id": 4, "item" : ["Apple", "google", "IBM" ] }

输出表

Id	Index	Name
4	0	apple
4	1	google
4	2	ibm

查询

select * from json_table
(  
on 
  (
      select Name.jsonextractvalue("$.id.[*]) as memberid,
      Name
      from table_data 
  )
using rowexpr("$.name[*]"]
colexpr("")

) as A(member_id,index,name)

Answer 1

使用 JSONExtractValue / JSONExtract

WITH T AS (
SELECT CAST(name.JSONExtractValue('$.id') AS INTEGER) AS id,
  CAST(name.JSONExtract('$.item[*]') AS VARCHAR(4096)) AS itemlist
FROM  table_data
)
SELECT id, token_ndx-1 AS "Index", Name 
FROM TABLE(REGEXP_SPLIT_TO_TABLE(
T.id,
SUBSTRING(T.itemlist FROM 3 FOR LENGTH(T.itemlist)-4), /* remove [" and "] */
'","',  /* split at "," sequences */
'c') 
RETURNS(id INTEGER, token_ndx INTEGER, Name VARCHAR(100))) AS split;

或者使用 JSON_Table：

WITH T AS (
  SELECT id, itemlist
  FROM JSON_Table
    (ON (SELECT "S.id" AS Dummy, Name FROM table_data)
     USING ROWEXPR('$')
     COLEXPR('[ {"jsonpath" : "$.id", "type" : "INTEGER"},
                {"jsonpath" : "$.item", "type" : "VARCHAR(4096)"}
              ]')
    ) AS jt(Dummy, id, itemlist)
)
SELECT id, token_ndx-1 AS "Index", Name 
FROM TABLE(REGEXP_SPLIT_TO_TABLE(
 T.id,
 SUBSTRING(T.itemlist FROM 3 FOR LENGTH(T.itemlist)-4), /* remove [" and "] */
 '","', /* split at "," sequences */
 'c')
RETURNS(id INTEGER, token_ndx INTEGER, Name VARCHAR(100))) AS split;