SQL is the abbreviation of Structured Query Language, which is a domain-specific language to manage relational databases. SQL is meant to perform various tasks on the data stored in the databases. SQL is now used as a standard database query language in all relational databases like Oracle, MySQL, Postgresql, SQL server, MS Access, Informix, and Sybase, etc.
SQL was developed in the 1970s by Raymond FF. Chamberlin who worked at IBM. It was first known as SEQUEL and was designed to retrieve data from the quasi-relational database systems of the old IBM.
SQL soon got established as a standardized language which is used to manage all types of relational databases. SQL is now the primary tool of not only the database administrators but also the developers who write scripts for data integration and also by data analysts who need to run analytical queries.
The primary uses or SQL include, but not limited to:
- Modifying data tables and the index structures
- Adding data
- Updating or deleting the data rows
- Retrieving information subsets from the database for transaction processing.
- Analytics applications.
SQL based database querying
Database queries are in the form of commands written as SQL statements like select, insert, add, delete, update, alter, create and truncate, etc. SQL is the de facto standard for relational databases since after its emergence in the 1970s. Each column in the relational database tables corresponds to specific categories of data like customer name or address etc. The rows contain data values against the intersecting columns.
The official SQL standard is as announced by the ANSI (American National Standards Institute) back in 1986 as well as that of ISO (International Organization for Standardization). There had been many updates released by these bodies since then.
SQL commands and syntax
There are various SQL commands, which are primarily divided into two main categories as:
- Data manipulation language (DML) and
- Data definition language (DDL)
There are different statements, controls, and security measures in each. DML vocabulary is primarily used in retrieving data and manipulating it whereas the DDL statements are more to define the database structure and modify it when needed. Transaction controls help in processing transactions and to ensure that all transactions are completed in an intended way or rolled back if any problems occur. Security statements of SQL are used to control the database access and also to create user permissions and roles. As per RemoteDBA.com, SQL syntaxes are codes to write various statements for the above purposes.
- Data integration – One of the major applications of SQL is for writing scripts for data integration scripts. These are created by the developers as well as database administrators.
- Analytical querying – Data analysts make use of SQL to set and run analytical queries to get an insightful understanding of the data.
- Information retrieval – Another major application of SQL is to retrieve the information subsets within the database for transaction processing.
- Other major applications – Apart from the above, SQL is also used to modify the index structures as well as database tables. Users can also add, update, edit, and delete the rows of data using SQL.
Benefits of SQL
There are various advantages offered by the Structured Query Language, which makes it the most focused programming query language in terms of database administration.
- No coding – SQL is easy to manage by anyone without the need for writing any coding as in case of custom development.
- Well defined standards – As discussed above, MySQL standards are set by ANSI and ISO. There are no such standards for the non-SQL databases.
- Portable – SQL can be used anywhere as system-level programming and for servers or even the mobile applications.
- Interactive programming language – Domain language to be used for database communications and to get answers to the most complex questions.
- Multiple data view – Using SQL, users can get multiple views of a database structure and also the databases of a wide range of users.
Disadvantages of SQL
Along with many benefits as discussed above, SQL has a few disadvantages too as below:
- Complicated interface – For users, SQL interface may seem to be a bit difficult at the initial stages.
- Limited control – The programmers using SQL may not get complete access to the database due to some hidden business rules.
- Implementation difficulties – Some databases get to the proprietary extensions of standard SQL to ensure vendor lock-ins.
- Cost – The initial costs of some SQL versions make it a bit difficult for entry-level programmers to use it.
There are different categories of SQL commands to perform different functions. These include the creation of database objects, data populating to database tables, manipulating objects, updating data, deleting data, security database access, performing queries, and full database administration. Major categories to name are:
- Data Definition Language or DDL
- Data Manipulation Language or DML
- Data Query Language or DQL
- Data Control Language or DCL
- Transactional control command
- Data administration command etc.
A query is basically an inquiry to a database to fetch some information. A query is raised to a database through an API or the command prompt.
The basic DDL commands are CREATE TABLE, CREATE INDEX, CREATE VIEW, ALTER TABLE, ALTER INDEX, ALTER VIEW, DROP INDEX, DROP TABLE, DROP VIEW, etc.
DML acts as a crucial part in SQL in order for manipulation of data in the relational database objects. The basic commands in DML are INSERT, UPDATE, and DELETE.
Data Query Language (DQL) comprises of only a single command for RDBMS users as SELECT. It is accompanied by various clauses and options to help compose and run different queries on any relational database.
DCL SQL commands are to let the users gain access to individual data within a database. These commands help create objects related to user access and control distribution of the privileges among different users. Some of such commands are ALTER PASSWORD, CREATE SYNONYM, REVOKE, GRANT, etc. You may find these commands coming grouped with various other commands in various forms.
Commands for data administration are meant for the users to run audits and analysis on operations inside a database. It can be of help in analyzing the performance of systems. Major commands in data administration are START AUDIT and STOP AUDIT. You shouldn’t get confused database administration with data administration. The overall administration of the database is DBA which is which envelops various level commands including data administration commands.
Transactional commands include COMMIT, ROLLBACK, SAVEPOINT, SET TRANSACTION etc.
Above given is an overview of SQL programming, and there are more things to learn and practice if someone really wants to master the art of database administration.