PostgreSQL INSERT statement.

Preamble

PostgreSQL INSERT statement is used to insert one or more records into a table in PostgreSQL.

The syntax for the INSERT statement

The syntax for PostgreSQL INSERT statement when inserting a record(s) using VALUES keyword

INSERT INTO table
(column1, column2,... )
VALUES
(expression1 | DEFAULT, expression2 | DEFAULT,... ),
(expression1 | DEFAULT, expression2 | DEFAULT,... ),
…;

Or:

The syntax for INSERT statement when inserting a single record using the DEFAULT VALUES keyword in PostgreSQL

INSERT INTO table
(column1, column2,... )
DEFAULT VALUES;

Or:

The syntax for INSERT statement when inserting multiple records using a subquery in PostgreSQL

INSERT INTO table
(column1, column2,... )
SELECT expression1, expression2,...
FROM source_table
[WHERE conditions];

Parameters and arguments of the statement

• table – A table for inserting records.
• column1, column2 – Columns in the table for inserting values.
• expression1 | DEFAULT, expression2 | DEFAULT – Used in the first syntax. These values are assigned to the columns in the table. If expression1 is specified then column1 will be assigned the value expression1, column2 will be assigned the value expression2, and so on. If DEFAULT is specified then the corresponding column will be filled with the default value.
• DEFAULT VALUES – Used in the second syntax. All columns will be filled with their default values.
• source_table – To be used in the third syntax. This is the source table when inserting data from another table.
• WHERE conditions – Optional. Used in the third syntax. These are the conditions that must be met to insert the records.

Note:

• When inserting records into a table using PostgreSQL, the INSERT operator must specify the value for each column NOT NULL.
• You can omit a column in PostgreSQL operator INSERT if the column allows NULL values.

Example using VALUES keyword

The easiest way to create a PostgreSQL INSERT query to get a list of values using the VALUES keyword.
For example:

INSERT INTO contacts
(contact_id, last_name, first_name, country)
VALUES
(250, 'Abramova', 'Irina', DEFAULT);

This PostgreSQL statement INSERT will cause a single record to be inserted into the contacts table. This new record will have contact_id 250, last_name ‘Abramova’, first_name ‘Irina’, and any default value for the country field.
You can use the above syntax to insert more than one record at a time.
For example:

INSERT INTO contacts
(contact_id, last_name, first_name, country)
VALUES
(250, 'Abramova', 'Irina', DEFAULT),
(251, 'Arbatova', 'Vitalina', 'Russia');

This PostgreSQL operator INSERT will insert two records into the contacts table. The first record will have contact_id 250, last_name ‘Abramova’, first_name ‘Irina’ and any default value for the country field . The second entry will have contact_id 251, last_name ‘Arbatova’, first_name ‘Vitalina’ and country ‘Russia’.
This will be equivalent to the next two INSERT operators:

INSERT INTO contacts
(contact_id, last_name, first_name, country)
VALUES
(250, 'Abramova', 'Irina', DEFAULT);

INSERT INTO contacts
(contact_id, last_name, first_name, country)
VALUES
(251, 'Arbatova', 'Vitalina', 'Russia');

Example using the DEFAULT VALUES keyword

In PostgreSQL, you can also insert a record into a table using DEFAULT VALUES syntax.
For example:

INSERT INTO contacts
(contact_id, last_name, first_name, country)
DEFAULT VALUES;

This PostgreSQL statement INSERT will cause one record to be inserted into the contacts table. This new record will be created with default values for the fields contact_id, last_name, first_name, and country.

Example using a subquery

You can also create more complex PostgreSQL statements INSERT using subqueries.
For example:

INSERT INTO contacts
(last_name, first_name)
SELECT last_name, first_name
FROM customers
WHERE customer_id > 3500;

By placing the SELECT operator in the INSERT operator, you can quickly perform several insertion operations.
With this type of insertion, you can check the number of lines to be inserted. You can define the number of rows to be inserted by executing the next PostgreSQL SELECT operator before inserting it.

SELECT count(*)
FROM customers
WHERE customer_id > 3500;

PostgreSQL: Insert Into | Course

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