PostgreSQL – TABLES
Tables are fundamental database objects used to store structured data in rows and columns. They are the primary means of organizing and managing data within a relational database. Tables define the structure of data and provide a framework for storing, retrieving, and manipulating information.
Creating a Table: To create a table in PostgreSQL, you use the CREATE TABLE statement. You specify the table name, column names, and data types for each column.
CREATE TABLE table_name( column1_name data_type,column2_name data_type, ... );
For example, creating a simple employees table:
CREATE TABLE employees( employee_id serial PRIMARY KEY,first_name varchar(50),last_name varchar(50),hire_date date );
Inserting Data: You use the INSERT INTO statement to add data to a table.
INSERT INTO table_name (column1_name, column2_name, ...) VALUES (value1, value2, ...);For example:
INSERT INTO employees (first_name, last_name, hire_date)VALUES ('John', 'Doe', '2023-01-15');
Querying Data: You can retrieve data from a table using the SELECT statement.
SELECT column1_name, column2_name, ... FROM table_name WHERE condition;For example:
SELECT first_name, last_name FROM employees WHERE hire_date > '2023-01-01';Updating Data: To modify existing data, you use the UPDATE statement.
UPDATE table_name SET column1_name = new_value1, column2_name = new_value2, ... WHERE condition;Deleting Data: To remove rows from a table, you use the DELETE statement.
DELETE FROM table_name WHERE condition;Dropping a Table: To remove a table and its data, you use the DROP TABLE statement.
DROP TABLE table_name;These are some of the basic operations you can perform with tables in PostgreSQL. Tables are central to organizing, storing, and manipulating data within a database, and they form the foundation for building relational database structures.