Hi ,
I have the following requirement .
I need to join two tables based on condition 1 and pick field A from table2
and based on condition 2 and pick field b from table2.
Please find below my query.
Insert INTO TABLEB
SELECT SR.COLUMNA FROM TABLEA SR LEFT JOIN TABLE B ML
ON SR.COLUMNA = ML.COLUMNA
UNION ALL
SELECT SR.COLUMNB FROM TABLE A SR LEFT JOIN TABLEB ML
ON SR.COLUMNB = ML.COLUMNA
WHERE ML.COLUMNA IS NULL
AND SR.COLUMNB IN NOT NULL
GROUP BY SR.COLUMNA
I have a doubt regarding the use of union all .Is it better to use union all or is there any better way to do THIS.
I would like to mention that i have around 40 million rows .so performance is my main concern.
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