[ako]

That is not a SQL mistake, but an implementation choice. Most modern databases can determine where indexes should be added, and add these automatically. E.g.: https://www.oracle.com/news/connect/oracle-database-automati...

[akoboldfrying]

This is news to me. Can any other DBs do this?

(I only skimmed -- far too much "Joan explains that" to signal ratio.)

[ako]

SQL server: https://learn.microsoft.com/en-us/sql/relational-databases/a...

Interesting read on a project implementing this for Postgres: https://pganalyze.com/blog/automatic-indexing-system-postgre...

[sharadov]

Not for postgres or mysql.