What Is SQL?

Đã đăng vào - Cập Nhật Lần Cuối vào

Dynamic websites are spreading fast on the World Wide Web since databases can handle most of their content. The introduction of SQL programming language has made Database management, a complex procedure, easy. SQL stands for Structured Query Language, and as the name depicts, it is responsible for editing and querying information kept in a particular database management system. It helps to query and manipulate data in certain relational databases using proprietary extensions. The ubiquity and ease of SQL have made many non-relational databases or NoSQL stores to accept some subsets of SQL or make private SQL-like query languages.

However, SQL has not always been the preferred universal language for all relational databases. Since its inception, SQL has had particular strikes that worked against it. Many ancient PHP developers and researchers thought that SQL would never be practical in a database. However, they were all wrong. Most of them hold on to their earlier belief asserting that since SQL is easy and readily available, its price should not be as high.

Life before SQL

Before the invention of SQL, there were rigid navigational programming interfaces that helped databases to function. Developers designed them using a network schema referred to as a Committee on Data Systems Languages (Codasyl) data model. Codasyl was the consortium that brought about the COBOL programming language that began in 1959 and its database language extensions that came into effect a decade later.

A PHP developer had to navigate through sets to get records, an indication of too many relationships. The previous hierarchical databases permitted a database to belong to only one set. However, network databases can work with a record that belongs to multiple sets. Database programmers thought that this was a lot of work, though there was improved efficiency in execution time. Experts indicated that performing a query such as IDMS in a Codasyl database consumed less computer memory and less time as compared to querying relational databases through SQL.

Freelancer has a lot of PHP projects that you can bid on to practice more.

History of SQL

The origin of SQL dates back to the 1970s when PHP developers created a new database software in IBM laboratories. To manage the data in System R, developers created the SQL language. It was originally called SEQUEL, a name that is used to date as an alternative pronunciation of SQL but was later renamed to read SQL. The Relational Software, later called Oracle, released a modified version called Oracle V2 after seeing the commercial potential of SQL. In its third decade since inception, SQL is known to offer flexibility to its users through supporting various distributed databases. Such are the databases that can run on an array of computer networks at a go.

Having received certification from ISO and ANSI, SQL has become a standard database query language, by an array of significant database applications available on the internet. It works in both academic and industry fields, as well as corporate and individual servers. Since database technology has advanced so greatly, SQL-based applications are easily available to the common user. The affordability has been brought about by the introduction of an array of open-source database solutions that include PostgreSQL, Firebird, SQLite, and MySQL among many others.

IBM was not fast enough to enact a relational database to protect the revenues of Codasyl database DB/IMS. When IBM started to implement System R, its development team (Ray Boyce and Don Chamberlin) was not working under Codd, and they departed from Alpha relational language to come up with their language known as Structured English Query Language (Sequel). Before IBM released its innovative product, Larry Ellison, an American Entrepreneur, integrated the language in the Oracle Database using Sequel publications from IBM as the specifications. Sequel would later change to SQL to avoid violating international trademark laws.

It was not easy to train and hire Codasyl database programmers and designers, and this made SQL (and Sequel) look more attractive. Since SQL became very attractive in the 1980s, most of the PHP developers then used a SQL query processor and embedded it on the Codasyl databases. This dismayed Codd whose feeling was that relational databases should be designed from scratch.

Access Freelancer and find how to use custom CSS in your WordPress site.      

Relational databases and SQL

Why would a PHP developer give up a database query that doubles memory and execution speed? Two reasons: portability and ease of development. None of the reasons mattered in 1980 apart from memory requirements and performance. However, the improvement of computer hardware and the reduction in the cost of the same made people stop caring about memory and execution speed, and they focused more on development cost. Most of the developers opined that Moore’s Law preferred relational databases instead of Codasyl databases. Relational databases contributed to the reduction in development time, but many developers wanted portability to be enhanced.

SQL Standard

SQL Standard has undergone numerous changes in recent years, and these changes have added many new functionalities such as XML support, recursive queries, triggers, standardized sequences, and regular expression matching and much more. Since SQL Standard is voluminous, it has a lot of database solutions that refer to it such as PostgreSQL and MySQL to execute the entire standard. The database behavior for indexes and file storage has a shallow description in many cases, and it is up to the vendors and PHP developers to decide the behavior of the database. This explains the reason why various SQL implementations are seldom compatible though they have similar bases.

SQL language elements

SQL is founded on various elements. Most of the commands in the SQL language database management systems are executed via explicit SQL command-line interface (CLI) to ensure the convenience of SQL developers. Some of the SQL elements include:

Clauses: These are components of queries and statements

Expressions: They can produce tables or scalar valuables which contain rows and columns of data

Predicates: They help in specifying conditions, which aid in limiting effects of queries and statements, or altering the flow of the program

Queries: Given certain criteria, a query helps in retrieving data

Statements: If a PHP developer has statements, he/she can control program flow, diagnostics, transactions, sessions, and connections. Developers use SQL to send queries to any server that stores databases from a client program. The server responds by processing the SQL statements and sending responses to the client program. Therefore, users can execute a wide range of data manipulation iterations from easy data inputs to complex queries.

If you need to know the best practices in PHP, find them on Freelancer.

SQL queries

SQL queries are the most critical and most essential operations in SQL. A PHP developer can search his/her database for any information through an SQL query. The SELECT statement helps in executing SQL queries. Several clauses help in specifying an SQL query such as:

WHERE - helps in defining rows where the search will be conducted. The WHERE clause will erase all rows which are false.

FROM - determines the table to conduct the search

ORDER BY - helps in ordering SQL results to avoid returning them in a random order.

SQL data manipulation

SQL tables require data manipulation which allows PHP developers to modify new information, delete existing values, or update them. The INSERT statement helps in adding new rows and columns to an already developed table. Any new row can contain information from the beginning or can have a NULL value.

Stored procedures

The SELECT statement has a declarative nature that prevents a PHP developer from getting to levels he/she may want. Stored procedures are facilities that are present in most databases. Unfortunately, most of the databases use extensions to the ISO/ANSI SQL standards.

The comment section below is open for you to give your views pertaining SQL.

Đã đăng 14 tháng 11, 2017


Designer // Writer // Creative

Tom is a Design Correspondent for Freelancer.com. He is currently based in Melbourne and spends most of his non-work moments trying to find the best coffee.

Bài báo kế tiếp

11 Technologies Transforming The Database