Inserting data into the table

PostgreSQL is a powerful, open-source object-relational database system. One of the fundamental operations that you'll need to learn when working with databases is how to insert data into a table. This tutorial will guide you through the process step by step, explaining all the necessary details to understand how to insert data into a PostgreSQL table.

Creating a Table

Before we can insert data into a table, we need to have a table. For this tutorial, let's create a simple table named students. This table will have three columns: id, name, and age.

In PostgreSQL, you can create a new table using the CREATE TABLE statement. The syntax is as follows:

CREATE TABLE table_name (
    column1 datatype,
    column2 datatype,
    column3 datatype,
   ....
);

Let's use this to create our students table:

CREATE TABLE students (
    id SERIAL PRIMARY KEY,
    name VARCHAR(100),
    age INT
);

In this SQL statement, SERIAL is an auto-incrementing integer, VARCHAR is a variable length string, and INT is an integer. PRIMARY KEY is a constraint that enforces the uniqueness of the id column.

Inserting Data

Now that we have a table, we can begin to insert data. In PostgreSQL, we use the INSERT INTO statement to insert data into a table. The syntax is as follows:

INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);

Let's insert some data into our students table:

INSERT INTO students (name, age)
VALUES ('John Doe', 20), 
       ('Jane Doe', 22),
       ('Jim Doe', 19);

In this SQL statement, we're inserting three rows into the students table. We don't need to specify a value for the id column because it's an auto-incrementing integer.

Verifying the Insertion

To make sure our data was inserted correctly, we can retrieve it using the SELECT statement. The syntax is as follows:

SELECT column1, column2, ...
FROM table_name;

Let's retrieve all data from our students table:

SELECT *
FROM students;

This SQL statement will return all rows from the students table. The * is a wildcard character that means "all columns".

Conclusion

In this tutorial, you learned how to create a table in PostgreSQL and how to insert data into it. You also learned how to retrieve the inserted data to verify its correctness. These are fundamental skills you'll need when working with databases, and with practice, they'll soon become second nature.