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POhow to remove correlated subquery
 

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  1. POhow to remove correlated subquery
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    <p>I'd like to rewrite this query so as not to use the correlated subquery -- but do achieve the same output from the query.</p> <pre><code>CREATE TABLE "TABLE_1" ( "SITE_ID" NUMBER(*,0), "USER_ID" NUMBER(*,0), "REC_ID" NUMBER, "REPORT_DATE" DATE ) ; CREATE TABLE "TABLE_2" ( "SITE_ID" NUMBER, "NOTE_DATE" DATE, "NOTES" VARCHAR2(2000 BYTE), "USER_ID" NUMBER, "REC_ID" NUMBER ) ; CREATE TABLE "TABLE_3" ( "SITE_ID" NUMBER, "NOTE_DATE" DATE, "HELP_NOTES" VARCHAR2(2000 BYTE), "USER_ID" NUMBER, "REC_ID" NUMBER ) ; REM INSERTING into TABLE_1 Insert into TABLE_1 (SITE_ID,USER_ID,REC_ID,REPORT_DATE) values (1,6165,121,to_date('17-APR-10','DD-MON-RR')); Insert into TABLE_1 (SITE_ID,USER_ID,REC_ID,REPORT_DATE) values (1,6165,121,to_date('01-MAY-10','DD-MON-RR')); Insert into TABLE_1 (SITE_ID,USER_ID,REC_ID,REPORT_DATE) values (1,6165,121,to_date('08-MAY-10','DD-MON-RR')); Insert into TABLE_1 (SITE_ID,USER_ID,REC_ID,REPORT_DATE) values (1,6165,121,to_date('24-APR-10','DD-MON-RR')); Insert into TABLE_1 (SITE_ID,USER_ID,REC_ID,REPORT_DATE) values (1,6165,121,to_date('15-MAY-10','DD-MON-RR')); Insert into TABLE_1 (SITE_ID,USER_ID,REC_ID,REPORT_DATE) values (1,6165,121,to_date('05-JUN-10','DD-MON-RR')); Insert into TABLE_1 (SITE_ID,USER_ID,REC_ID,REPORT_DATE) values (1,6165,121,to_date('22-MAY-10','DD-MON-RR')); Insert into TABLE_1 (SITE_ID,USER_ID,REC_ID,REPORT_DATE) values (1,6165,121,to_date('29-MAY-10','DD-MON-RR')); REM INSERTING into TABLE_2 Insert into TABLE_2 (SITE_ID,NOTE_DATE,NOTES,USER_ID,REC_ID) values (1,to_date('13-APR-10','DD-MON-RR'),'Notes - we need stuff.',6165,121); REM INSERTING into TABLE_3 Insert into TABLE_3 (SITE_ID,NOTE_DATE,HELP_NOTES,USER_ID,REC_ID) values (1,to_date('17-MAY-10','DD-MON-RR'),'Entry #1',1932,121); Insert into TABLE_3 (SITE_ID,NOTE_DATE,HELP_NOTES,USER_ID,REC_ID) values (1,to_date('12-MAY-10','DD-MON-RR'),'Entry #2',6005,121); Insert into TABLE_3 (SITE_ID,NOTE_DATE,HELP_NOTES,USER_ID,REC_ID) values (1,to_date('25-MAY-10','DD-MON-RR'),'Entry #3',1932,121); ALTER TABLE "TABLE_1" MODIFY ("REC_ID" NOT NULL ENABLE); -------------------------------------------------------- -- Constraints for Table TABLE_2 -------------------------------------------------------- ALTER TABLE "TABLE_2" MODIFY ("SITE_ID" NOT NULL ENABLE); ALTER TABLE "TABLE_2" MODIFY ("REC_ID" NOT NULL ENABLE); -------------------------------------------------------- -- Constraints for Table TABLE_3 -------------------------------------------------------- ALTER TABLE "TABLE_3" MODIFY ("SITE_ID" NOT NULL ENABLE); ALTER TABLE "TABLE_3" MODIFY ("REC_ID" NOT NULL ENABLE); </code></pre> <p>THe query is as follows: </p> <pre><code>SELECT TABLE_1.REC_ID, TO_CHAR(table_1.REPORT_DATE, 'DD-MON-YY HH:MI:SS') report_date, ( SELECT MAX(table_3.NOTE_DATE) AS MAX_DATE FROM table_3 WHERE table_3.REC_ID = table_1.REC_ID AND table_3.NOTE_DATE &lt;= table_1.REPORT_DATE ) notes_max_date FROM table_1 ORDER BY To_date(table_1.REPORT_DATE, 'DD-MON-YY HH:MI:SS') </code></pre> <p>And the output should be as follows:</p> <pre><code>REC_ID REPORT_DATE NOTES_MAX_DATE ---------------------- ------------------ ------------------------- 121 17-APR-10 12:30:00 121 24-APR-10 12:30:00 121 01-MAY-10 12:30:00 121 08-MAY-10 12:30:00 121 15-MAY-10 12:30:00 12-MAY-10 121 22-MAY-10 12:30:01 17-MAY-10 121 29-MAY-10 12:30:01 25-MAY-10 121 05-JUN-10 12:30:00 25-MAY-10 8 rows selected </code></pre> <p>The output needs to be 8 rows and include the nulls in the NOTES_MAX_DATE columm. Thanks!</p>
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    1. PO
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      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USskaffman
    1. USshawno
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    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
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      1. PTAnswer
    1. This table or related slice is empty.
    1. This table or related slice is empty.
 

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