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Differences between UNIQUE and DISTINCT in select statements
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Answer Posted / rob reid
Howard Cheon is correct. They are THE SAME. There is no
difference.
The following is from the Oracle 9i SQL Reference (Note the
statement "these two keywords are synonymous" - that means
they mean the same thing):
DISTINCT | UNIQUE
Specify DISTINCT or UNIQUE if you want Oracle to return
only one copy of each set of duplicate rows selected (these
two keywords are synonymous). Duplicate rows are those with
matching values for each expression in the select list.
Restrictions on DISTINCT and UNIQUE Queries
When you specify DISTINCT or UNIQUE, the total number of
bytes in all select list expressions is limited to the size
of a data block minus some overhead. This size is specified
by the initialization parameter DB_BLOCK_SIZE.
You cannot specify DISTINCT if the select_list contains LOB
columns.
| Is This Answer Correct ? | 59 Yes | 6 No |
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