Comments (1)
Does a query like 'SELECT column1 FROM <table with 20 columns>' take 10 times longer than a query like 'SELECT column1 FROM <table with 1 column>' even if the data volume returned by both queries is the same? I would like to know how long both queries take to send all data to ODBC-Loader.
It needs to read all rows to know the column has only NULL value. If it can know it beforehand, it removes the column from the query or it uses FILLER option in COPY statement to ignore the column.
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