Finding part of string and extracting data between delimiter using BigQuery SQL

Question

I have a column like this:

String_to_Extract
A~S1_B~S2_C~S11
A~S1_B~S3_C~S12
C~S13_A~S11_B~S4

The part before the "~" should be the column name. The part after the "~" should be the row value. This is separated by a "_". Therefore, the result should look like this:

String_to_Extract	A	B	C
A~S1_B~S2_C~S11	S1	S2	S11
A~S1_B~S3_C~S12	S1	S3	S12
C~S13_A~S11_B~S4	S11	S4	S13

Here is my approach:

SELECT
String_to_Extract,
SUBSTRING(String_to_Extract, INSTR(Advertiser, "A~")+2, ?) AS A,
SUBSTRING(String_to_Extract, INSTR(Advertiser, "B~")+2, ?) AS B,
SUBSTRING(String_to_Extract, INSTR(Advertiser, "C~")+2, ?) AS C,
From Table

How do I get the part between the ~ and next _ for each column?

Would be glad about help!

Answer 1

One approach uses REGEXP_EXTRACT :

SELECT
    REGEXP_EXTRACT(String_to_Extract, r"(?:^|_)A~([^_]+)") AS A,
    REGEXP_EXTRACT(String_to_Extract, r"(?:^|_)B~([^_]+)") AS B,
    REGEXP_EXTRACT(String_to_Extract, r"(?:^|_)C~([^~]+)") AS C
FROM yourTable;

Answer 2

Consider below approach (BigQuery)

select * from (
  select String_to_Extract, col_val[offset(0)] as col, col_val[offset(1)] as val
  from your_table, unnest(split(String_to_Extract, '_')) kv,
  unnest([struct(split(kv, '~') as col_val)])
)
pivot (any_value(val) for col in ('A', 'B', 'C'))   

If applied to sample data in your question - output is

Answer 3

You can also use this approach which orders the splitted item first and then picks the values:

select 
   split(ordered[safe_offset(0)], '~')[safe_offset(1)] as A,
   split(ordered[safe_offset(1)], '~')[safe_offset(1)] as B,
   split(ordered[safe_offset(2)], '~')[safe_offset(1)] as C
 from (
    select 
        array(select _ from unnest(split(Advertiser, '_') ) as _ order by 1) as ordered
    from dataset.table
)