Causes of top SQL

This is an interview question from a netizen. When asked about the general conditions of top SQL, the answer is different for different companies and DBAs participating in different stages of the project. Generally, the top SQL generation phase includes the system design phase (Table Structure Design), coding implementation phase (SQL writing), and SQL review and Optimization phase. The following factors are involved: system designers, developers, and DBAs may encounter top SQL statements when any problem occurs. Therefore, it is not necessarily the DBA's responsibility to have performance problems in a project, however, excellent DBAs can eliminate potential risks.

The causes of top SQL are described as follows:
1. unreasonable Table Structure Design
2. The index creation is unreasonable.
3 unnecessary table Association
4 implicit data type conversion causes no index
5. Use a table function without specifying the appropriate hints.
6. do not bind variables
7. The statistical information of tables and indexes is outdated.