Please take this survey to help us learn more about how you use third party tools. Your input is greatly appreciated!

i have 2 tables ,A and A_backup,now i want to drop the backup table if the original exists ?

i am extracting tables weekly from a different Db ,before extraction i rename original tables to backup,and after extraction delete the backup table ,How could this be achived

Answers

  • Jim_KnicelyJim_Knicely Administrator
    edited March 23

    Maybe something lilke this?

    dbadmin=> CREATE TABLE a (c INT); -- Original table
    CREATE TABLE
    
    dbadmin=> INSERT INTO a SELECT 1; -- Original table
     OUTPUT
    --------
          1
    (1 row)
    
    dbadmin=> SELECT COPY_TABLE('a', 'a_backup'); -- Make backup pre-extraction
                         COPY_TABLE
    -----------------------------------------------------
     Created table a_backup.
    Copied table a to a_backup
    
    (1 row)
    
    dbadmin=> INSERT INTO a SELECT 2; -- Extracted data added to original table
     OUTPUT
    --------
          1
    (1 row)
    
    dbadmin=> SELECT COUNT(*) FROM a;
     COUNT
    -------
         2
    (1 row)
    
    dbadmin=> SELECT COUNT(*) FROM a_backup;
     COUNT
    -------
         1
    (1 row)
    
    dbadmin=> \! vsql -Atc "SELECT 'SELECT ''DROP TABLE ' || table_schema || '.' || table_name || ' CASCADE;'' sql FROM dual WHERE (SELECT COUNT(*) FROM ' ||  table_schema || '.' || REPLACE(table_name, '_backup', '') || ') > (SELECT COUNT(*) FROM ' || table_schema || '.' || table_name || ');' FROM tables WHERE table_name ILIKE '%backup';" | vsql -At | vsql # Run the DDL
    DROP TABLE
    
    dbadmin=> \dt a*
                  List of tables
     Schema | Name | Kind  |  Owner  | Comment
    --------+------+-------+---------+---------
     public | a    | table | dbadmin |
    (1 row)
    

    But why not extract into a new table first then swap the tables?

    dbadmin=> \dt a*
                  List of tables
     Schema | Name | Kind  |  Owner  | Comment
    --------+------+-------+---------+---------
     public | a    | table | dbadmin |
    (1 row)
    
    dbadmin=> SELECT * FROM a;
     c
    ---
     1
     2
    (2 rows)
    
    dbadmin=> CREATE TABLE a_temp LIKE a INCLUDING PROJECTIONS; -- Load new data here
    CREATE TABLE
    
    dbadmin=> INSERT INTO a_temp SELECT 1;
     OUTPUT
    --------
          1
    (1 row)
    
    dbadmin=> INSERT INTO a_temp SELECT 2;
     OUTPUT
    --------
          1
    (1 row)
    
    dbadmin=> INSERT INTO a_temp SELECT 3;
     OUTPUT
    --------
          1
    (1 row)
    
    dbadmin=> COMMIT;
    COMMIT
    
    dbadmin=> ALTER TABLE a, a_temp, temp RENAME TO temp, a, a_temp; -- Swap the tables!
    ALTER TABLE
    
    dbadmin=> SELECT * FROM a;
     c
    ---
     1
     2
     3
    (3 rows)
    
    dbadmin=> SELECT * FROM a_temp;
     c
    ---
     1
     2
    (2 rows)
    
    dbadmin=> DROP TABLE a_temp;
    DROP TABLE
    

Leave a Comment

BoldItalicStrikethroughOrdered listUnordered list
Emoji
Image
Align leftAlign centerAlign rightToggle HTML viewToggle full pageToggle lights
Drop image/file

Can't find what you're looking for? Search the Vertica Documentation, Knowledge Base, or Blog for more information.