The following query is used to find the number of blocks that contain rows:
I have run this and do not understand how the two substring arguments detect occupancy.
Can somebody help me to understand this?
Thanks in advance.
Below is the ROWID format fro Oracle7
BBBBBBBB is the block number,
RRRR is the slot(row) number, and
FFFF is a file number.
So in yur query you are counting the no. of occupied blocks in all the files.
However the ROWID format has been changed in Oracle8
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