Welcome to our blog post on SQL Server concepts! In this article, we will explore some important concepts that every SQL Server developer should be familiar with. Let’s dive in!

1. Functions vs Stored Procedures

One of the fundamental differences between a function and a stored procedure in SQL Server is their usage. Functions can be used in SQL statements anywhere in the WHERE, HAVING, or SELECT section, whereas stored procedures cannot. Additionally, functions that return tables can be treated as another rowset, allowing them to be used in JOINs with other tables. On the other hand, stored procedures cannot be used in this manner.

2. Subqueries and their Properties

A subquery, also known as a sub-select, allows a SELECT statement to be executed within the body of another SQL statement. It is executed by enclosing it in a set of parentheses. Subqueries are commonly used to return a single row as an atomic value or to compare values against multiple rows using the IN keyword. They can be found in the column list of a SELECT statement, as well as in the FROM, GROUP BY, HAVING, and ORDER BY clauses of a T-SQL statement. Subqueries can also be used as parameters to function calls.

3. Different Types of Joins

Joins are used to combine data from multiple tables based on a related column between them. There are several types of joins:

• Cross Join: A cross join produces the Cartesian product of the tables involved in the join. It combines each row from the first table with every row from the second table.
• Inner Join: An inner join displays only the rows that have a match in both joined tables.
• Outer Join: An outer join includes rows even if they do not have related rows in the joined table. There are three types of outer joins: left outer join, right outer join, and full outer join.
• Self Join: A self join occurs when a table joins to itself. It is often used in scenarios where a hierarchical reporting structure exists.

4. Primary Keys and Foreign Keys

Primary keys are unique identifiers for each row in a table. They must contain unique values and cannot be null. They are essential for maintaining data integrity in relational databases. On the other hand, foreign keys are used to establish relationships between tables and ensure referential integrity. They manifest the relationship between tables by referencing the primary key of another table.

5. User-defined Functions

User-defined functions allow developers to define their own T-SQL functions. These functions can accept zero or more parameters and return a single scalar data value or a table data type. There are three types of user-defined functions:

• Scalar User-defined Function: This type of function returns one of the scalar data types and is similar to functions in other programming languages.
• Inline Table-Value User-defined Function: An inline table-value function returns a table data type and can be used as a parameterized, non-updateable view of the underlying tables.
• Multi-Statement Table-Value User-defined Function: This function also returns a table and supports multiple T-SQL statements to build the final result. It can be used to create a parameterized, non-updateable view of the data in the underlying tables.

Understanding these concepts will greatly enhance your SQL Server development skills. Stay tuned for more informative articles on SQL Server!

Thank you for reading!