Thank you very much for reading my post.
can you please explain me what is differences between 1 index for
one column and one index for multiple columns ?
In addition to what Ryan Bobko has already said about SELECT
statements, I should point out that the existence of indexes on a
table affects the performance of updates on the table. For example,
if you have three indexes on a table, each insert of a row into the
table will result in inserts into the three indexes as well as the
base table. Same with deletes - each row deleted from the table must
be deleted from the indexes as well. For UPDATE statements, the
indexes are updated only if the index columns are updated, so with
three indexes on a table an UPDATE statement could result in zero,
one, two or three indexes being updated.
- Jeff Lichtman
[EMAIL PROTECTED]
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