SQL - What is Tables?
In SQL, tables are the fundamental structure used to store and organize data. They consist of rows and columns, representing records and attributes, respectively.
Table: A table is a collection of related data organized in a structured format. It consists of rows and columns and is defined with a unique name.
Column: A column, also referred to as a field, represents a specific attribute or piece of data within a table. Each column has a name and a data type that determines the kind of data it can store (e.g., integer, string, date).
Row: A row, also known as a record or tuple, represents a single instance or entry within a table. It contains data values corresponding to each column in the table.
Primary Key: A primary key is a column or combination of columns that uniquely identifies each row in a table. It ensures data integrity and facilitates efficient data retrieval. Primary keys are typically used as reference points for relationships between tables.
Foreign Key: A foreign key is a column or combination of columns in one table that refers to the primary key of another table. It establishes relationships between tables and maintains data integrity.
Data Types: Data types define the kind of data that can be stored in a column, such as integer, string, date, or boolean. Different database management systems support various data types, and they have specific storage requirements and constraints.
NULL: NULL represents the absence of a value in a column. It is distinct from an empty string or zero and is used when a value is unknown, missing, or not applicable.
Constraints: Constraints are rules defined on a table to enforce data integrity. Common constraints include the primary key constraint, foreign key constraint, unique constraint, and not-null constraint.
Index: An index is a database structure that improves the speed of data retrieval operations. It is created on one or more columns of a table to allow faster searching and sorting based on those columns.
Normalization: Normalization is the process of organizing data in a database to eliminate redundancy and dependency issues. It involves dividing tables into smaller, well-defined structures to reduce data duplication and improve data integrity.
Schema: A schema is a logical container that holds database objects, including tables, views, indexes, and constraints. It defines the structure, organization, and relationships between these objects.
Understanding these terms will provide you with a solid foundation for working with SQL tables and designing efficient database structures. Keep in mind that the syntax and features related to tables may vary slightly depending on the specific database management system you are using.