如何从 Redshift/SQL 中的 json 字符串字段解析检索值

Question

I have a row that looks like this:

---

id | json_list | expected_result

"1" | [{"id":"1", "text":"text1"},{"id":"3", "text":"text3"}] | "text1"

"2" | [{"id":"2", "text":"text2"},{"id":"3", "text":"text3"}] | "text2"

---

I want to retrieve the "text" field based on the id column. How can I achieve that in AWS Redshift? I know Redshift has some json functions and it needs to be paired with some kind of loop condition, but I wasn't sure if it's possible in SQL

Answer 1

Please let me know, If I have understood your question correctly or not. Because the data is a bit confusing.

Id column value - 2 Your Json value - [{"id":"1", "text":"text1"},{"id":"3", "text":"text3"}] Expected Result - text1

Solution ->

Step 1 - Iterating through various JSON Elements

select json_extract_array_element_text('[{"id":"1", "text":"text1"},{"id":"3", "text":"text3"}]',1)

Step 2 - Parsing key,Value Pairs in a particular JSON Element

select json_extract_path_text(json_extract_array_element_text('[{"id":"1", "text":"text1"},{"id":"3", "text":"text3"}]',1),'text')

So, Suppose I have a table -

create table dev.gp_test1_20200731
(
id int,
json_list varchar(1000),
expected_result varchar(100)
)

Inserting Data -

insert into dev.gp_test1_20200731
values
(1,'[{"id":"1", "text":"text1"},{"id":"3", "text":"text3"}]', 'text1'),
(2,'[{"id":"2", "text":"text2"},{"id":"3", "text":"text3"}]', 'text2')

How does the data look like -

This is how the query would be -

select json_extract_path_text(json_extract_array_element_text(json_list,1),'text')
from dev.gp_test1_20200731
where id = 2

Result -

But, It is not a good practice of storing JSON's in Redshift.

Documentation on why - Link