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How to read array data into one column

I have a table (tbl1) where a column is used as array data:

I would like to read this data so it shows ID|email as columns:

Also, I would like to know how to read it back from a list (pic2) to an array (pic1).

Answers

  • Please review the below link.. It should help

    https://www.vertica.com/blog/vertica-quick-tip-dynamically-split-string/

  • LenoyJLenoyJ Employee
    edited September 10

    For the first request, you can also use the StringTokenizerDelim function:

    dbadmin=> create table tbl1 (id varchar, col_array varchar);
    CREATE TABLE
    

    .

    dbadmin=> copy tbl1 from stdin;
    Enter data to be copied followed by a newline.
    End with a backslash and a period on a line by itself.
    >> A|email1,email2,email3
    >> B|email6,email7
    >> C|email8,email9,email10,email11
    >> \.
    

    .

    dbadmin=> select * from tbl1;
     id |           col_array
    ----+-------------------------------
     A  | email1,email2,email3
     C  | email8,email9,email10,email11
     B  | email6,email7
    (3 rows)
    

    .

    dbadmin=> SELECT ID, v_txtindex.StringTokenizerDelim(col_array, ',') over (partition by ID) from tbl1;
     ID |  words  |             input
    ----+---------+-------------------------------
     A  | email1  | email1,email2,email3
     A  | email2  | email1,email2,email3
     A  | email3  | email1,email2,email3
     B  | email6  | email6,email7
     B  | email7  | email6,email7
     C  | email8  | email8,email9,email10,email11
     C  | email9  | email8,email9,email10,email11
     C  | email10 | email8,email9,email10,email11
     C  | email11 | email8,email9,email10,email11
    (9 rows)
    

     
     
    For the second request, you can use the ListAgg function:

    dbadmin=> create table tbl2 as SELECT ID, v_txtindex.StringTokenizerDelim(col_array, ',') over (partition by ID) from tbl1;
    CREATE TABLE
    

    .

    dbadmin=> select * from tbl2;
     ID |  words  |             input
    ----+---------+-------------------------------
     B  | email6  | email6,email7
     B  | email7  | email6,email7
     A  | email1  | email1,email2,email3
     A  | email2  | email1,email2,email3
     A  | email3  | email1,email2,email3
     C  | email8  | email8,email9,email10,email11
     C  | email9  | email8,email9,email10,email11
     C  | email10 | email8,email9,email10,email11
     C  | email11 | email8,email9,email10,email11
    (9 rows)
    

    .

    dbadmin=> select id, listagg(words) from tbl2 group by id;
     id |            listagg
    ----+-------------------------------
     C  | email8,email9,email10,email11
     B  | email6,email7
     A  | email1,email2,email3
    (3 rows)
    
  • Thank you SruthiA and LenoyJ! The first part worked great using both your ideas. I have issue with second part - combining list structure back into array: ERROR: Function listagg(varchar) does not exist, or permission is denied for listagg(varchar)
    Are those user created functions?

  • LenoyJLenoyJ Employee
    edited September 10

    Whoops, I should've mentioned that ListAgg was introduced in 9.1.1-4.
     
    If you can't upgrade - you can try using Group_Concat function instead from the Strings package on our github. You'll have to build it from source for your platform though. Instructions here:
    https://github.com/vertica/Vertica-Extension-Packages/tree/master/strings_package
     
    Example on how to use:
    https://github.com/vertica/Vertica-Extension-Packages/blob/master/strings_package/examples/group_concat.sql

  • Thanks for the tip! We will be upgrading most likely next year, but I will try with Group_Concat.

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