Wednesday, January 9, 2013

CREATE a table from another table


You can also create a table from an existing table by copying the existing table's columns.
It is important to note that when creating a table in this way, the new table will be populated with the records from the existing table (based on the SQL SELECT Statement).

Syntax #1 - Copying all columns from another table

The syntax for CREATING a table by copying all columns from another table is:
CREATE TABLE new_table
  AS (SELECT * FROM old_table);
For Example:
CREATE TABLE suppliers
AS (SELECT *
    FROM companies
    WHERE id > 1000);
This would create a new table called suppliers that included all columns from the companies table.
If there were records in the companies table, then the new suppliers table would also contain the records selected by the SELECT statement.

Syntax #2 - Copying selected columns from another table

The syntax for CREATING a table by copying selected columns from another table is:
CREATE TABLE new_table
  AS (SELECT column_1, column2, ... column_n FROM old_table);
For Example:
CREATE TABLE suppliers
  AS (SELECT id, address, city, state, zip
      FROM companies
      WHERE id > 1000);
This would create a new table called suppliers, but the new table would only include the specified columns from the companies table.
Again, if there were records in the companies table, then the new suppliers table would also contain the records selected by the SELECT statement.

Syntax #3 - Copying selected columns from multiple tables

The syntax for CREATING a table by copying selected columns from multiple tables is:
CREATE TABLE new_table
  AS (SELECT column_1, column2, ... column_n
      FROM old_table_1, old_table_2, ... old_table_n);
For Example:
CREATE TABLE suppliers
  AS (SELECT companies.id, companies.address, categories.cat_type
      FROM companies, categories
      WHERE companies.id = categories.id
      AND companies.id > 1000);
This would create a new table called suppliers based on columns from both the companies and categories tables.

Frequently Asked Questions


Question: How can I create an SQL table from another table without copying any values from the old table?
Answer: To do this, the syntax is:
CREATE TABLE new_table
  AS (SELECT * FROM old_table WHERE 1=2);
For Example:
CREATE TABLE suppliers
  AS (SELECT * FROM companies WHERE 1=2);
This would create a new table called suppliers that included all columns from the companies table, but no data from the companies table