Question 90229 in PostgreSQL Question posted in
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SQL query multiple values in just one cell – Postgresql

Hello I am kinda new to sql. Just wanna know if this is possible via sql:

Table: (Multiple values are in just 1 cell.)

COLUMN 1 COLUMN 2
"2023-01-01", "2023-01-02", "2023-01-03" "User A, User B, User C"

Needed Output:

COLUMN 1 COLUMN 2
2023-01-01 User A
2023-01-02 User A
2023-01-03 User A
2023-01-01 User B
2023-01-02 User B
2023-01-03 User B
2023-01-01 User C
2023-01-02 User C
2023-01-03 User C

Basically, each date from the row is assigned to all users in that same row. Any help or tip will be appreciated.

Thank you!
Screenshot of data/required table

I have no idea yet on how to go around this

Tags:

5

Answers


  1. 0

    Because implementation details van change on different DBMS’s, here is an example of how to do it in MySQL (8.0+):

    WITH column1 as (
   SELECT TRIM(SUBSTRING_INDEX(SUBSTRING_INDEX(column1,',',x),',',-1)) as Value
   FROM test
   CROSS JOIN (select 1 as x union select 2 union select 3 union select 4) x
   WHERE x <= LENGTH(Column1)-LENGTH(REPLACE(Column1,',',''))+1
  ),
  column2 as (
   SELECT TRIM(SUBSTRING_INDEX(SUBSTRING_INDEX(column2,',',x),',',-1)) as Value
   FROM test
   CROSS JOIN (select 1 as x union select 2 union select 3 union select 4) x
   WHERE x <= LENGTH(Column2)-LENGTH(REPLACE(Column2,',',''))+1
  )
SELECT * 
FROM column1, column2;

    see: DBFIDDLE

    NOTE:

    • The CROSS JOIN, with only 4 values should be expanded when more than 4 items exist.
    • There is not data type connected to the values that are fetched. This implementation does not know that "2023-01-08" is, sorry CAN BE, a date. It just sticks to strings.
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  2. 0

    In sql server this can be done using string_split

    select x.value as date_val,y.value as user_val
 from test a
CROSS APPLY string_split(Column1,',')x
CROSS APPLY string_split(Column2,',')y
order by y.value,x.value

date_val    user_val
2023-01-01  User A
2023-01-02  User A
2023-01-03  User A
2023-01-03  User B
2023-01-02  User B
2023-01-01  User B
2023-01-01  User C
2023-01-02  User C
2023-01-03  User C

    db fiddle link

    https://dbfiddle.uk/YNJWDPBq

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  3. 0

    In mysql you can do it as follows :

    WITH dates as ( 
  select TRIM(SUBSTRING_INDEX(_date, ',', 1)) AS 'dates'
  from _table
  union 
  select TRIM(SUBSTRING_INDEX(SUBSTRING_INDEX(_date, ',', 2), ',', -1)) AS 'dates'
  from _table
  union
  select TRIM(SUBSTRING_INDEX(_date, ',', -1)) AS 'dates'
  from _table
),
users as
  ( select TRIM(SUBSTRING_INDEX(user, ',', 1)) AS 'users'
  from _table
  union 
  select TRIM(SUBSTRING_INDEX(SUBSTRING_INDEX(user, ',', 2), ',', -1)) AS 'users'
  from _table
  union
  select TRIM(SUBSTRING_INDEX(user, ',', -1)) AS 'users'
  from _table
)
select *
from dates, users
order by dates, users;

    check it here : https://dbfiddle.uk/_oGix9PD

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  4. 0

    You can use the string_to_array function to get all parts of a string as elements of an array, then use the unnest function on that array to get the desired result, check the following:

    select col1,
  unnest(string_to_array(replace(replace(COLUMN2,'"',''),', ',','), ',')) as col2
from 
(
  select unnest(string_to_array(replace(replace(COLUMN1,'"',''),', ',','), ',')) as col1
         , COLUMN2
  from table_name
) T
order by col1, col2

    See demo

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  5. 0

    We can use a combination of STRING_TO_ARRAY with UNNEST and LATERAL JOIN here:

    SELECT col1.column1, col2.column2
FROM
(SELECT UNNEST(
  STRING_TO_ARRAY(column1,',')
) AS column1 FROM test) col1
LEFT JOIN LATERAL
(SELECT UNNEST(
  STRING_TO_ARRAY(column2,',')
) AS column2 FROM test) col2
ON true
ORDER BY col2.column2, col1.column1;

    Try out: db<>fiddle

    STRING_TO_ARRAY will split the different dates and the different users into separate items.

    UNNEST will write those items in separate rows.

    LATERAL JOIN will put the three dates together with the three users (or of course less/more, depending on your data) and so creates the nine rows shown in your question. It works similar to the CROSS APPLY approach which will do on a SQL Server DB.

    The ORDER BY clause just creates the same order as shown in your question, we can remove it if not required. The question doesn’t really tell us if it’s needed.

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