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What is the minimum number of rows required to create an index?

I created a script to find the selectivity of each column for all tables. In some tables with less than 100 rows, column selectivity is more than 50%. Where Selectivity = Significant Values ​​/ Total Number of Rows. Are these columns suitable for the index? Or, can you tell me the minimum requirement for the number of rows to create an index?

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You can index any column - the question is whether it makes any sense and whether this index will be used ...

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IMHO, any table with less than 5000 rows should not be analyzed for power if the DBMS is running on a server.

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