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A Visual Explanation of SQL Joins

A Visual Explanation of SQL Joins
I love the concept, though, so let's see if we can make it work. Assume we have the following two tables. Table A is on the left, and Table B is on the right. We'll populate them with four records each. id name id name -- ---- -- ---- 1 Pirate 1 Rutabaga 2 Monkey 2 Pirate 3 Ninja 3 Darth Vader 4 Spaghetti 4 Ninja Let's join these tables by the name field in a few different ways and see if we can get a conceptual match to those nifty Venn diagrams. There's also a cartesian product or cross join, which as far as I can tell, can't be expressed as a Venn diagram: SELECT * FROM TableA CROSS JOIN TableB This joins "everything to everything", resulting in 4 x 4 = 16 rows, far more than we had in the original sets.

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Prepared Statements in PHP and MySQLi : Matt Bango's Journal This article is intended for readers who have experience using PHP and MySQL. You should also have a general understanding of databases and programming (both procedural and object-oriented) as well as how to use PHP to execute a simple query to MySQL. I will not cover how to install PHP or MySQL, however at the end of the article are some links to help you get started with the installation process and for some further reading on the subject. I will be covering the basics of prepared statements in PHP and MySQLi and why you should consider using them in your own code as well as some technical explanation as to why you should use them. Introduction If you are like me and most other people, you probably have not taken the time to learn about web security when you first started writing server-side code.

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Slow in the Application, Fast in SSMS? An SQL text by Erland Sommarskog, SQL Server MVP. Last revision: 2013-08-30. This article is also available in Russian, translated by Dima Piliugin. Introduction Five simple database design tips A flawed database can affect all areas of your application, so getting the design right is of paramount importance. Check out Builder's five simple design tips, and share some of your own. If an enterprise’s data is its lifeblood, then the database design can be the most important part of an application. Volumes have been written on this topic, and entire college degrees have been built around it. However, as has been said time and time again here on, there’s no teacher like experience. MySQLi, what’s the difference between standard queries and prepared statements? You may have heard of prepared statements, but don’t quite understand the differences. In this post I’m going to try and help you with that. Well, with your standard query, you would get your information, escape it for safety, build your query and execute. <?php/* instantiate our class, and select our database automatically */$sql = mysqli('localhost','user','password','database'); /* let's assume we've just received a form submission. so we'll receive the information, and we'll escape it */$name = $sql->real_escape_string($_POST['name']);$age = $sql->real_escape_string($_POST['age']);$email = $sql->real_escape_string($_POST['email']); /* build the query, we'll use an insert this time */$query = "INSERT INTO `tablename` VALUES ('$name','$age','$email');"; /* execute the query, nice and simple */$sql->query($query) or die($query.'

How to share data between stored procedures An SQL text by Erland Sommarskog, SQL Server MVP. Most recent update 2013-11-02. Introduction This article tackles two related questions: How can I use the result set from one stored procedure in another, also expressed as How can I use the result set from a stored procedure in a SELECT statement? How can I pass a table data in a parameter from one stored procedure to another?

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Using the SQL WHERE clause - learn how to filter rows in your database queries at In our introduction to the SQL SELECT statement we saw how to select specific columns from a table. In this article we will see how the WHERE clause can be used to select specific rows from the table that match certain specified criteria or conditions. The WHERE clause is an optional clause in the following SQL statements: SELECT statmentsDELETE statementsUPDATE statements This makes the WHERE clause a major foundation to build upon when learning SQL as it is so frequently used. Comparison Operators

Client Requests Not Redirecting to Failover Partner Hi Jimmy, In this case, I am initiating the failover by clicking the failover button on the database properties, mirroring form from within Management Studio. It behaves no differently if I stop the SQL Server service and force a failover that way. I am killing the connection at the database. I don't have the rights to cycle the web service. If killing the session at the database level does not accomplish the desired effect and I need to cycle the web service, let me know. Ten Common Database Design Mistakes No list of mistakes is ever going to be exhaustive. People (myself included) do a lot of really stupid things, at times, in the name of “getting it done.” This list simply reflects the database design mistakes that are currently on my mind, or in some cases, constantly on my mind. I have done this topic two times before. If you’re interested in hearing the podcast version, visit Greg Low’s super-excellent SQL Down Under. I also presented a boiled down, ten-minute version at PASS for the Simple-Talk booth.

Graphs Most non-trivial data is hierarchical. Customers have orders, which have line items, which refer to products, which have prices. Population samples have subjects, who take tests, which give results, which have sub-results and norms. Web sites have pages, which have links, which collect hits, which distribute across dates and times. With such data, we know the depth of the hierarchy before we sit down to write a query. The depth of the hierarchy of tables fixes the number of JOINs we need to write.

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