15 May 2017 Aldo Zelen Oracle Top-N Queries for Absolute Beginners It's common to run a query using only part of a dataset – for example, the top 100 salespeople in a company. In this article, we'll see how to use Oracle's Top-N query method to query just these rows. Top-N queries retrieve a defined number of rows (top or bottom) from a result set. In other words, they find the best or worst of something – the ten best selling cars in a certain region, the five most popular routers, the 20 worst-performing stores, etc. Read more 18 Apr 2017 Aldo Zelen Understanding Numerical Data Types in SQL Working with databases of any kind means working with data. This data can take a couple of predefined formats. As you start on your learning path with LearnSQL.com, you will start to understand SQL's different data types. In this article, we will cover different variations of the SQL numeric data type. We'll also examine some functions that convert data from one type to another. Creating tables is the first step in any SQL coding project. Read more 4 Apr 2017 Aldo Zelen 5 Books That Will Grow Your SQL Skills Which books will help you build your database skills? We look at five awesome SQL books. There’s a common saying that “all wise men read books”. I would say that all professionals read books – particularly those related to their field. There are many books about databases and SQL; most are tied to specific vendors (DB2, Oracle, MS SQL) but there are also plenty that are vendor-neutral. In this article, I’m going to review a few books that I would recommend to SQL learners at various levels of proficiency. Read more 16 Feb 2017 Aldo Zelen A Day in the Life of a SQL Developer What is a SQL developer? And what does a SQL developer do? Describing a “typical” day for a SQL developer is not easy. When your daily work is using various technologies to create interesting database-oriented products, very few days are alike! Each day brings a new and intriguing challenge. Nevertheless, I’ll have a go at explaining what everyday things a SQL developer might do. Morning: Arrive at Work What does a SQL developer do after arriving at the office? Read more 3 Jan 2017 Aldo Zelen How to Recognize SQL Text Data Type How can you store textual information in database tables? Thanks to this post, you’ll learn the characteristics of every text data type in SQL Note: This post is intended for readers familiar with SQL data definition language (DDL) and the DDL CREATE statement. To learn more about DDL, check out LearnSQL.com. Most data types are classified as NUMERIC, CHARACTER, or DATE. In this post, we’re going to focus on each CHARACTER or text data type in SQL. Read more 28 Dec 2016 Aldo Zelen Refine Results with SQL Set Operators Using UNION, UNION ALL, EXCEPT, and INTERSECT to manage SQL query results. The function of SQL set operators is pretty simple; they allow us to combine results from different SQL queries into one result set. The best way to understand how set operators work is to use visual methods like the Venn diagram. For those of you not familiar with Venn diagrams, they are two circles that represent items or collections of items. Read more 13 Dec 2016 Aldo Zelen How to Learn SQL: 6 Ideas for Newbies Learning a new skill can be a daunting task, especially in programming. SQL is not immune to this. Luckily, with the Internet and the explosion of programming-related information out there, there are a lot of options you can use to undergo your SQL training! But we then come to a new roadblock. Where to begin? How will we know which option is best for our budget, skill level, and schedule? Read more 6 Dec 2016 Aldo Zelen SQL Errors: Five Common SQL Mistakes As you learn SQL, watch out for these common coding mistakes You’ve written some SQL code and you’re ready to query your database. You input the code and …. no data is returned. Instead, you get an error message. Don’t despair! Coding errors are common in any programming language, and SQL is no exception. In this article, we’ll discuss five common mistakes people make when writing SQL. The best way to prevent mistakes in SQL is practice. Read more 6 Dec 2016 Aldo Zelen Five Common SQL Syntax Errors As you learn SQL, watch out for these common coding mistakes You’ve written some SQL code and you’re ready to query your database. You input the code and …. no data is returned. Instead, you get an error message. Don’t despair! Coding mistakes are common in any programming language, and SQL is no exception. In this post, we’ll discuss five common SQL syntax errors people make when writing code. Read more 27 Sep 2016 Aldo Zelen A Gentle Introduction to Common SQL Window Functions Mastering SQL analytical functions is a necessity for an aspiring BI/DWH professional. In this article, we'll explore the history of SQL in a BI environment. We'll also introduce some of the more common SQL analytical functions, including RANK, LEAD, LAG, SUM, and others. SQL can be used for business intelligence (BI) applications that combine data retrieval, analysis, and computation. These computations are more complex than what we see in OLTP systems. Read more «« « 1 2 3 » »»