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Sunday, September 11, 2011

SQL: CREATE

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 SELECT Statement).

Syntax #1 - Copying all columns from another table

The basic syntax 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 basic syntax 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 basic syntax 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 andcategories tables.

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