Oracle SQL query Optimization with multiple filters and create table

Question

My select query is running for 15 hours and still running so I cancelled it. How can I optimize my query?

CREATE TABLE W_PURCH_RCPT_FS_tmp
AS

    SELECT RCV.TRANSACTION_ID,
           PO.RELEASE_DATE,
           NVL (ASL.PROCESSING_LEAD_TIME, MTL.FULL_LEAD_TIME)
               AS PROCESSING_LEAD_TIME
      FROM obia_ui.PO_ASL_ATTRIBUTES@betsy.world@dsn_310      ASL,
           obia_ui.MTL_SYSTEM_ITEMS_B@betsy.world@dsn_310      MTL,
           obia_ui.RCV_TRANSACTIONS@betsy.world@dsn_310       RCV,
           obia_ui.PO_RELEASES_ALL@betsy.world@dsn_310         PO,
           obia_ui.PO_LINES_ALL@betsy.world@dsn_310           LINES,
           obia_ui.PO_LINE_LOCATIONS_ALL@betsy.world@dsn_310   LOC,
           obia_ui.PO_HEADERS_ALL@betsy.world@dsn_310          HEAD
     WHERE  RCV.CREATION_DATE > '30-JUN-2016'
            AND MTL.INVENTORY_ITEM_ID = LINES.ITEM_ID
           AND MTL.ORGANIZATION_ID = LOC.SHIP_TO_ORGANIZATION_ID
           AND LINES.PO_LINE_ID = LOC.PO_LINE_ID
           AND ASL.USING_ORGANIZATION_ID = LOC.SHIP_TO_ORGANIZATION_ID
           AND ASL.ITEM_ID = LINES.ITEM_ID
           AND ASL.VENDOR_ID = HEAD.VENDOR_ID
           AND ASL.VENDOR_SITE_ID = HEAD.VENDOR_SITE_ID
           AND RCV.TRANSACTION_ID = PO.PO_RELEASE_ID
           ;

I expect that query to finish shorter.

Answer 1

First of all you have to master explain plan concept to optimize a query in Oracle. After understanding explain plans I would suggest to go for table by table. Starting from the first table check how it performs on an explain plan. By this way you can figure out the indexes that need to be created. Sometimes there's no way to create a useful index. In that case splitting the data into smaller chunks (tables) may help. Also Oracle has a parallel query running capabilities. You can take advantage of this feature too.