Utilizing the Power of SQL for Data Management
The speed and efficiency of accessing data can make or break an application. If it takes too long to store, manipulate, or retrieve data, your users will abandon ship in search of a better solution. There’s no time to waste in today’s business environment, so your application must manage data quickly and efficiently. That’s where the power of SQL can be utilized.
SQL (Structured Query Language) is the standard language for managing relational databases that are commonly used in the development of applications and websites. Developed in the 1970s, SQL is a mature language that meets ANSI/ISO standards. A SQL database provides a structured table environment of related data which makes it easy to identify, access, and manage.
SQL Statements are used to perform the functions required for database management. A statement is the smallest unit of work that a SQL server will perform. A few of the most commonly used SQL statements are SELECT, UPDATE, DELETE, and INSERT INTO. Let’s take a brief look at each of these.
The SELECT statement is used to select and return data from a database. A simple SELECT may return one or more results in a results table. Combined with SQL clauses like TOP or WHERE, the SELECT statement can be used to return specific results. The SELECT DISTINCT statement may also be used to return distinct (unique) values. The SELECT statement is a retrieval function that performs no additional action on the data.
The UPDATE statement is used to modify records that exist in a data table. To perform an update of all records in a table, a simple UPDATE statement may be used. In many cases, an UPDATE is combined with a WHERE clause to restrict the update of data to a specified record or dataset.
An INSERT INTO statement is used to insert new records into a data table. This statement may not be combined with clauses such as WHERE or DISTINCT since there is no logical necessity for performing such functions.
To remove data from a table, the DELETE statement is used. As with any deletions, be cautious about your statement before executing. A simple DELETE statement will purge all data from a table. Combined with the WHERE clause, a DELETE statement may only remove specified records.
A SQL query is a request for data composed of statements and clauses to obtain a desired result. It may retrieve data or execute an action such as insert, delete, or update. It may also perform summaries and calculations. Queries can be automated to perform routine functions for an application and return results for real-time processing or batch routines. The power of efficient queries is evident when utilized effectively in applications.
Conditional clauses are portions of a SQL query that may be combined with SQL statements to return desired results. Although the statements above may be used alone to create simple queries such as SELECT * FROM [TABLE], conditional clauses provide the necessary control for sufficiently managing data. There are a few conditional clauses that may be used to restrict query performance or arrange results. Here’s a brief explanation of the three most frequently used clauses.
The WHERE clause is used for filtering or limiting query results. It is followed by a logical condition that returns a true or false value. When a query is executed, SQL will examine each row of data and return results where the conditional clause value is true.
Unlike WHERE, the HAVING clause performs aggregate functions on the data and is always coupled with the GROUP BY clause. The HAVING clause is executed after SQL loads the query results to memory. The GROUP BY clause is used to group results prior to performing the aggregate functions commanded and returning a combined result.
The ORDER BY clause is used to sort results by one or more fields in ascending or descending order. Without specifying, the default sort order is ascending.
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