What is SQL?
Structured Query Language is a computer language that we use to interact with a relational database.SQL is a tool for organizing, managing, and retrieving archived data from a computer database. The original name was given by IBM as Structured English Query Language, abbreviated by the acronym SEQUEL. When data needs to be retrieved from a database, SQL is used to make the request. The DBMS processes the SQL query retrieves the requested data and returns it to us. Rather, SQL statements describe how a collection of data should be organized or what data should be extracted or added to the database.
- Data definition: It is used to define the structure and organization of the stored data and relationships among the stored data items.
- Data retrieval: SQL can also be used for data retrieval.
- Data manipulation: If the user wants to add new data, remove data, or modifying in existing data then SQL provides this facility also.
- Access control: SQL can be used to restrict a user’s ability to retrieve, add, and modify data, protecting stored data against unauthorized access.
- Data sharing: SQL is used to coordinate data sharing by concurrent users, ensuring that changes made by one user do not inadvertently wipe out changes made at nearly the same time by another user.
SQL also differs from other computer languages because it describes what the user wants the computer to do rather than how the computer should do it. (In more technical terms, SQL is a declarative or descriptive language rather than a procedural one.) SQL contains no IF statement for testing conditions, and no GOTO, DO, or FOR statements for program flow control. Rather, SQL statements describe how a collection of data is to be organized, or what data is to be retrieved or added to the database. The sequence of steps to do those tasks is left for the DBMS to determine.
Features of SQL:
- SQL may be utilized by quite a number of users, which include people with very little programming experience.
- SQL is a Non-procedural language.
- We can without difficulty create and replace databases in SQL. It isn’t a time-consuming process.
- SQL is primarily based totally on ANSI standards.
- SQL does now no longer have a continuation individual.
- SQL is entered into SQL buffer on one or extra lines.
- SQL makes use of a termination individual to execute instructions immediately. It makes use of features to carry out a few formatting.
- It uses functions to perform some formatting.
Rules for SQL:
- A ‘;’ is used to end SQL statements.
- Statements may be split across lines but keywords may not.
- Identifiers, operator names, literals are separated by one or more spaces or other delimiters.
- A comma(,) separates parameters without a clause.
- A space separates a clause.
- Reserved words can not be used as identifiers unless enclosed with double quotes.
- Identifiers can contain up to 30 characters.
- Identifiers must start with an alphabetic character.
- Characters and date literals must be enclosed within single quotes.
- Numeric literals can be represented by simple values.
- Comments may be enclosed between /* and */ symbols and maybe multi-line.
Role of SQL :
SQL plays many different roles:
- SQL is an interactive question language. Users type SQL instructions into an interactive SQL software to retrieve facts and show them on the screen, presenting a convenient, easy-to-use device for ad hoc database queries.
- SQL is a database programming language. Programmers embed SQL instructions into their utility packages to access the facts in a database. Both user-written packages and database software packages (consisting of document writers and facts access tools) use this approach for database access.
- SQL is a client/server language. Personal computer programs use SQL to communicate over a network with database servers that save shared facts. This client/server architecture is utilized by many famous enterprise-class applications.
- SQL is an Internet facts access language. Internet net servers that have interaction with company facts and Internet utility servers all use SQL as a widespread language for getting access to company databases, frequently through embedding SQL database get entry to inside famous scripting languages like PHP or Perl.
- SQL is a distributed database language. Distributed database control structures use SQL to assist distribute facts throughout many linked pc structures. The DBMS software program on every gadget makes use of SQL to speak with the opposite structures, sending requests for facts to get entry to.
- SQL is a database gateway language. In a pc community with a mixture of various DBMS products, SQL is frequently utilized in a gateway that lets in one logo of DBMS to speak with every other logo. SQL has for this reason emerged as a useful, effective device for linking people, pc packages, and pc structures to the facts saved in a relational database.
Finally, SQL is not a particularly structured language, especially when compared with highly structured languages such as C, Pascal, or Java. Instead, SQL statements resemble English sentences, complete with “noise words” that don’t add to the meaning of the statement but make it read more naturally. The SQL has quite a few inconsistencies and also some special rules to prevent you from constructing SQL statements that look perfectly legal but that don’t make sense.
Despite the inaccuracy of its name, SQL has emerged as the standard language for using relational databases. SQL is both a powerful language and one that is relatively easy to learn. So SQL is a database management language. The database administrator answerable for handling a minicomputer or mainframe database makes use of SQL to outline the database shape and manipulate get entry to to the saved data.