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PostgreSQL CREATE TABLE AS statement

10 September 2020

 

 

PostgreSQL CREATE TABLE AS statement

 

PostgreSQL CREATE TABLE AS statement is used to create a table from an existing table by copying columns of an existing table.

It is important to note that when creating a table this way, the new table will be filled with records from the existing table (based on the SELECT operator).

The syntax for CREATE TABLE AS in PostgreSQL

CREATE TABLE new_table AS
SELECT expressions
FROM existing_tables
[WHERE conditions];

Parameters and arguments of the statement

  • table_name – The name of the table you want to create.
  • expressions – Columns from existing_tables that you want to create in new_table. The definitions of the columns from these columns will be moved to the new_table you created.
  • existing_tables – Existing tables from which you can copy the column definitions and related entries (as suggested by WHERE).
  • WHERE conditions – Optional. Conditions that must be met to copy records to the new_table.

Note:

  • Column definitions from existing_tables will be copied to the new_table.
  • new_table will be filled with entries based on conditions in the WHERE proposal.

Consider the example of PostgreSQL CREATE TABLE AS, which shows how to create a table by copying all columns from another table.

CREATE TABLE current_inventory AS
SELECT *
FROM products
WHERE quantity > 0;

In this example, a new table named current_inventory will be created including all columns from the products table.

If the products table has records, the new current_inventory table will be filled with records returned by the SELECT operator. In other words, all entries from the product table with a number greater than 0 will be inserted into the current_inventory table when it is created.

Next Consider the example CREATE TABLE AS, which shows how to create a table by copying selected columns from multiple tables.
For example:

CREATE TABLE current_inventory AS
SELECT products.product_id, products.product_name, categories.category_name
FROM products
INNER JOIN categories
ON products.category_id = categories.category_id
WHERE products.quantity > 0;

In this example, a new table named current_inventory will be created based on the column definitions from the products and categories tables.

Again, the new current_inventory table will only add entries that satisfy the SELECT operator conditions.

PostgreSQL: Creating Tables with Constraints | Course

 
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