You've probably noticed that some of the technical SQL interview questions are similar to other SQL interview questions. This is due to the fact that one cannot function without the other. It's pointless to know the theory if you can't put it into practice, i.e., write SQL code. You must, on the other hand, convey the technical notions that underpin the code you built. While the SQL principles you need to know will vary depending on your position, years of experience, and the firm you want to work for, we've looked at a few that are applicable to all roles. While this is not an exhaustive list, you should be aware of the following if you are attending a SQL Data Science Interview.
SQL is an acronym for structured query language.
"Structured Query Language" stands for "Structured Query Language." It is a programming language that is used to create database structures, as well as retrieve and manipulate data from them.
Database with a relational structure
A relational database is one that uses the relational data model as its foundation. This signifies that the database is made up of relationships. Tables with columns, rows, and values are used to display these relationships. The relational database tries to reduce or eliminate data redundancy, resulting in data integrity and faster retrieval. Here, check the sql queries examples.
Normalization of the database
Database normalization is the process of structuring data in a database in order to satisfy the database's goals of data integrity, non-redundancy, and retrieval speed.
A view is a virtual table that contains data from one or more tables that are created as a result of a SQL operation.
Procedure that has been saved
A stored procedure is a piece of SQL code that saves one or more SQL statements and may be called and run whenever needed.
A trigger is a form of stored process that is unique. When a specific event occurs in the database, it is automatically executed (triggered).
Tables and Queries Joined
The inner connection
Only the rows where the data from one table matches the data from the second table are returned in an inner join.
outer join on the left
The left join is a table join that returns all rows from the left table and only the rows that match from the right table.
Outer right join
This join returns all of the rows from the right table as well as only the rows from the left table that match.
A complete outer join
The full outer join joins the data in such a way that the output includes all of the rows from one table as well as all of the rows from the other.
As a result, a Cartesian product is produced. This implies it will return all of the row combinations from one table as well as all of the row combinations from the other table.
This is a SQL command that combines the results of two queries into a single result. As a result, it will only display unique records.
We're all in this together.
This one combines the results of two or more inquiries as well. The only difference between UNION and UNION ALL is that UNION ALL will include duplicates as well.