Constraints on tables and columns allow you to enforce the data quality. In SQL, there are two ways of creating constraints on a table: inline and out of line.
In this article, I am going to explore these constraints and the advantages they have, as well as explain which one I recommend and why.
In this article, we’ll look at how an index can improve the query performance.
Indexes in Oracle and other databases are objects that store references to data in other tables. They are used to improve the query performance, most often the SELECT statement.
They aren’t a “silver bullet” – they don’t always solve performance problems with SELECT statements. However, they can certainly help.
Let’s consider this on a particular example.
A subquery is a powerful way to find the data you want to use for another query. They are often used in SELECT and UPDATE statements to make these queries more efficient and easier to maintain.
There are several different ways to use subqueries in UPDATE statements. Let’s take a look at each of them.