What is SQL?
SQL is Structured Query Language, which is a computer language for storing, manipulating and retrieving data stored in a relational database.
SQL is the standard language for Relational Database System. All the Relational Database Management Systems (RDMS) like MySQL, MS Access, Oracle, Sybase, Informix, Postgres and SQL Server use SQL as their standard database language.
Also, they are using different dialects, such as −
• MS SQL Server using T-SQL,
• Oracle using PL/SQL,
• MS Access version of SQL is called JET SQL (native format) etc.
Why SQL?
SQL is widely popular because it offers the following advantages −
• Allows users to access data in the relational database management systems.
• Allows users to describe the data.
• Allows users to define the data in a database and manipulate that data.
• Allows to embed within other languages using SQL modules, libraries & pre-compilers.
• Allows users to create and drop databases and tables.
• Allows users to create view, stored procedure, functions in a database.
• Allows users to set permissions on tables, procedures and views.
Rules:
SQL follows the following rules:
Structure query language is not case sensitive. Generally, keywords of SQL are written in uppercase.
Statements of SQL are dependent on text lines. We can use a single SQL statement on one or multiple text line.
Using the SQL statements, you can perform most of the actions in a database.
SQL depends on tuple relational calculus and relational algebra.
What is RDBMS?
RDBMS stands for Relational Database Management System. RDBMS is the basis for SQL, and for all modern database systems like MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access.
A Relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd
What is a table?
The data in an RDBMS is stored in database objects which are called as tables. This table is basically a collection of related data entries and it consists of numerous columns and rows.
What is a field?
Every table is broken up into smaller entities called fields. The fields in the CUSTOMERS table consist of ID, NAME, AGE, ADDRESS and SALARY.
A field is a column in a table that is designed to maintain specific information about every record in the table.
What is a Record or a Row?
A record is also called as a row of data is each individual entry that exists in a table.
What is a column?
A column is a vertical entity in a table that contains all information associated with a specific field in a table.
What is a NULL value?
A NULL value in a table is a value in a field that appears to be blank, which means a field with a NULL value is a field with no value.