What are the main parameters to consider when creating indexes for a database?

When creating indexes for a database, it is important to consider the following parameters:

• Choice of columns for indexing: index the columns that are frequently used in queries with filtering or sorting.
• Type of index: B-tree, hash index, full-text, etc., depending on the type of queries.
• Uniqueness: unique indexes ensure the uniqueness of values and can speed up searches.
• Size and composition of the index: overly large indexes slow down insert and update operations.
• Data cardinality: indexes are more effective on columns with a large variety of values.
• Order of columns in composite indexes: affects the ability to use the index in different queries.
• Frequency of data updates: if data changes frequently, indexes can become a bottleneck.

Example: if a query like SELECT * FROM users WHERE last_name = ? is frequently executed, it makes sense to create an index on the last_name column.