Tag Archive

Tag Archives for " SQL 201 "

Build Dynamic SQL in a Stored Procedure

Dynamic SQL

After reading this article you will understand the basics of dynamic SQL; how to build statements based on variable values, and how to execute those constructed statements using sp_executesql and EXECUTE() from within a stored procedure. All the examples for this lesson are based on Microsoft SQL Server Management Studio and the sample databases AdventureWorks […]

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Calculate a Running Total in SQL with Joins or Window Functions

There are several ways to calculate a running total in SQL.  In this article, we will cover two methods:  Joins, and Window Functions. We’ll first look at how to calculate the running total using an INNER JOIN.  By doing so, you’ll not only learn more about join conditions, but see how to take the result […]

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Joins versus Subqueries SQL Puzzle

Joins versus Subqueries

In this puzzle, we’re going to learn about joins versus subqueries.  In many queries you can substitute joins and subqueries.  Yet, since each has their strengths, it isn’t wise to do so.  Once you have worked through this puzzle you see some of the benefits and disadvantages of joins versus subqueries. Solving puzzles is a […]

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What is the difference between a subquery and inner join?

In this puzzle, we’re going to learn how to rewrite a subquery using inner joins.  Knowing about a subquery versus inner join can help you with interview questions and performance issues.  Though subqueries have unique abilities, there are times when it is better to use other SQL constructs such as joins. By reading this article […]

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Learn how to Work Joins and Messy Data

In this puzzle, we’re going to learn how to join dirty data using SQL Server.  Many times you’re forced to use someone else’s data.  Since it is their system and data, not yours, you can’t always fix the inconsistently formatted data before it is in the database. So how can you use it?  Do this […]

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Work with the AdventureWorks Bill of Materials using Subqueries

In this puzzle, we’re going to learn how to work with the AdventureWorks Bill of Materials table.  Companies use a BOM (Bill of Materials) to itemize the products that are used or contained in another product. Solving puzzles is a great way to learn SQL.  Nothing beats practicing what you’ve learned.  Once you have figured […]

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SQL Puzzle:  How to Calculate Moving Averages

In this puzzle, we’re going to learn how to calculate moving averages by working through a hypothetical stock market example. Solving puzzles is a great way to learn SQL.  Nothing beats practicing what you’ve learned.  Once you have figured out the puzzle, post you answer in the comments so we all can learn from one […]

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Rank Data with SQL

In this puzzle, we’re going to work through a problem to identify the top and bottom 25 percent to rank student scores. Solving puzzles is a great way to learn SQL.  Nothing beats practicing what you’ve learned. SQL Puzzle Question In today’s puzzle assume you’ve been asked by the head of the Mathematics department to […]

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Recursive CTEs Explained

Recursive CTE’s In this article we explore recursive CTE’s (Common Table Expressions).  Recursive CTEs are special in the sense they are allowed to reference themselves!  Because of this special ability, you can use recursive CTEs to solve problems other queries cannot.  Recursive CTEs are really good at working with hierarchical data such as org charts […]

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Non Recursive CTEs Explained and Why to Use Them

Introduction to Non Recursive CTEs In this article we explore non recursive CTEs (Common Table Expressions).  This is a broad class, and basically covers every form of CTEs except those that call themselves.  This other class is called the recursive CTEs; they are covered in the next article. If you’re unfamiliar with CTEs I would […]

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Introduction to Common Table Expressions (CTE’s)

Common Table Expressions or CTE’s for short are used within SQL Server to simplify complex joins and subqueries, and to provide a means to query hierarchical data such as an organizational chart.  In this set of articles, we’ll introduce you to common table expressions, the two types, and their uses.  In this article we’ll introduce […]

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What is the Difference between Inner and Outer Joins?

Both inner and outer joins can be used to combine data from two or more tables; however, there are some key differences!  Read this article to find out each command’s strengths and when to use them. To get the most of this and our other lessons be sure to practice using the examples! All the […]

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What is the Difference between a Primary Key and a Foreign Key?

Primary and Foreign Keys

In this article we learn the difference between a primary key and a foreign key, and why both are important to maintaining a relational database structure. All the examples for this lesson are based on Microsoft SQL Server Management Studio and the AdventureWorks2012 database.  You can get started using these free tools using my Guide Getting Started […]

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Is it possible to use Joins, Subqueries, and Unions in one Query?

A reader recently asked me to help them solve a problem combining data from multiple tables into a single result.  What was interesting was that the solution used the three ways to combine data that we have recently covered, namely:  JOINS, set operators, and subqueries. Given the comprehensive nature of this problem I thought it […]

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Get Ready to Learn SQL Server 23: Using Subqueries in the HAVING Clause

HAVING Clause Subquery

This is the fifth in a series of articles about subqueries.  In this article we discuss subqueries in the HAVING clause.  Other articles discuss their uses in other clauses. All the examples for this lesson are based on Microsoft SQL Server Management Studio and the AdventureWorks2012 database.  You can get started using these free tools using […]

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Using A Subquery in the FROM clause

Derived Tables in From Statement

This is the fourth in a series of articles about subqueries.  In this article we discuss using a subquery in the FROM clause.  Other articles discuss their uses in other clauses. All the examples for this lesson are based on Microsoft SQL Server Management Studio and the AdventureWorks2012 database.  You can get started using these free tools […]

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Using Subqueries in the WHERE Clause

Sub query in Where Clause

This is the third in a series of articles about subqueries.  In this article we discuss subqueries in the WHERE clause.  Other articles discuss their uses in other clauses. All the examples for this lesson are based on Microsoft SQL Server Management Studio and the AdventureWorks2012 database.  You can get started using these free tools […]

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Using Subqueries in the Select Statement

Subqueries in Select Statement

This is the second in a series of articles about subqueries.  In this article we discuss subqueries in the SELECT statement’s column list.  Other articles discuss their uses in other clauses. All the examples for this lesson are based on Microsoft SQL Server Management Studio and the AdventureWorks2012 database.  You can get started using these […]

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Learn SQL – Introduction to Subqueries

Introduction to Sub Queries

The purpose of this article is to introduce you to subqueries and some of their high-level concepts.  There are a lot of details to cover in order to learn sub queries, but you’ll see we cover those in depth in later articles. All the examples for this lesson are based on Microsoft SQL Server Management […]

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How do I combine results from more than one table?

Combine data in SQL

Many times in a relational database the information you want to show in your query is in more than one table.  This begs the question “How do you combine results from more than one table?” All the examples for this lesson are based on Microsoft SQL Server Management Studio and the AdventureWorks2012 database.  You can […]

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Learn to use Union, Intersect, and Except Clauses

Intersection, Exception, Union

Learn to use Union, Intersect, and Except Clauses The UNION, INTERSECT, and EXCEPT clauses are used to combine or exclude like rows from two or more tables.  They are useful when you need to combine the results from separate queries into one single result.  They differ from a join in that entire rows are matched […]

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