SQL (Structured Query Language) is most popular programming language and used for managing and manipulating relational databases. If you're a beginner, here are some fundamental concepts to get you started:
Databases: Basically Databases are organized collections of structured data. They can contain tables, views, indexes, and other objects.
Tables: Tables are like spreadsheets where data is stored. Each table consists of rows and columns. Rows represent individual records, and columns represent attributes or fields of those records.
Data Types: SQL supports various data types such as integers, strings, dates, and more. You specify the data type when creating a table to define what type of data can be stored in each column.
SQL Statements: Here are main SQL statements listed below:
SELECT: Used to retrieve data from one or more tables.
INSERT: Used to add new data into a table.
UPDATE: Used to modify existing data in a table.
DELETE: Used to remove data from a table.
Primary Key: A primary key is a unique identifier for each record in a table. Example: Emp_ID can be Primary Key for EMPLOYEE table.
Foreign Key: A foreign key is a column or set of columns in one table that refers to the primary key in another table. It establishes relationships between tables.
Indexes: Indexes are data structures used to improve the speed of data retrieval operations on a table. They are often created on columns that are frequently used in WHERE clauses.
Normalization: Normalization is the process of organizing data in a database to eliminate redundancy and improve data integrity. It involves breaking down tables into smaller, related tables.
Joins: SQL allows you to combine data from multiple tables using JOIN operations. Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.
WHERE Clause: The WHERE clause is used in SELECT, UPDATE, and DELETE statements to filter rows based on specific conditions.
ORDER BY Clause: The ORDER BY clause is used to sort the result set in ascending or descending order based on one or more columns.
GROUP BY Clause: GROUP BY clause is used with aggregate functions (e.g., SUM, COUNT, AVG) to group rows that share the same values in one or more columns.
Aggregate Functions: Functions like SUM, COUNT, AVG, MIN, and MAX to perform calculations on groups of rows.
Transactions: A transaction is a sequence of one or more SQL statements to perform some task. Transactions ensure data consistency and integrity.
Views: Views are virtual tables created by querying one or more tables. They can simplify complex queries and provide an abstracted view of the data.
References:
SQL Tutorial
SQL Courses
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