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(1)Do not index small tables. It may be more efficient to search the table in memory than to store an additional index structure.
(2)Avoid indexing a column or table that is frequently updated.
(3)Avoid indexing a column if the query will retrieve a significant proportion (for example, 25%) of the records in the table, even if the table is large. In this case, it may be more efficient to search the entire table than to search using an index.
(4)Avoid indexing columns that consist of long character strings.
kalvinspartan answered the question on July 4, 2018 at 17:11
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