Finished the Book

There is the following table. You need to select the row with the maximum date and other fields of that row.

In an ORACLE database, you need to delete a record from a table, but there are related records in other tables. In such cases, when attempting to delete, we get the ORA-022292 error.

When designing sufficiently large relational databases, a decision is often made to deviate from normal form - “denormalization”. In such cases, triggers can help ensure data integrity.

Given a sum, you need to select values from a list so that their sum matches the given amount.

Why does a query execute so slowly? Why are indexes not being used? Everyone has probably heard of EXPLAIN in PostgreSQL.

You need to check the validity of a Russian INN (Tax Identification Number).