Easy to ignore in Oracle

When we write SQL statements, we often ignore some details. The following is a summary of my own operations and materials. If there is something wrong, or there is a supplement.

When we write SQL statements, we often ignore some details. The following is a summary of my own operations and materials. If there is something wrong, or there is a supplement.

When we write SQL statements, we often ignore some details. The following is a summary of my own operations and materials. If there is something wrong or something wrong, hope to reply to me and learn from each other. Thank you!

1. When a full table scan is performed, and the number of records in the full table scan is more than 100, you need to create a correspondingIndexOrChange query ConditionsTo use index queries to avoid full table scans.

2. Use the like statement in the query as much as possible.Suffix fuzzy search. For example:
Select * from tablename where column_name like'% Name %'-- The index on column_name is not used

Select * from tablename where column_name like' Name %' -- Use the index on column_name

3. If the subquery or list after in contains more than five values, do not use in instead of exists; use not exists instead of not in.

4. Do not select useless fields.

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