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1
Write some guidelines for choosing the indexes in a table.
Answer
Do not index small relations
In general, index the primary key of a relation if it is not a key of the file organization
Add a secondary index to a foreign key if it is frequently accessed
Add a secondary index to any attribute that is heavily used as a secondary key
Add a secondary index on attributes that are frequently involved in:
(a) selection or join criteria
(b) ORDER BY
(c) GROUP BY
(d) other operations involving sorting (such as UNION or DISTINCT)
Add a secondary index on attributes involved in built-in aggregate functions, along with any attributes used for the built-in functions
Avoid indexing an attribute or relation that is frequently updated
Avoid indexing an attribute if the query will retrieve a significant proportion (for example 25%) of the tuples in the relation
Avoid indexing attributes that consist of long character strings
