CREATE TABLE AS creates a table and fills it with data computed by a SELECT command. The table columns have the names and data types associated with the output columns of the SELECT (except that you can override the column names by giving an explicit list of new column names).
CREATE TABLE AS bears some resemblance to creating a view, but it is really quite different: it creates a new table and evaluates the query just once to fill the new table initially. The new table will not track subsequent changes to the source tables of the query. In contrast, a view re-evaluates the underlying SELECT statements whenever it is queried.
If specified, the table is created as a temporary table. Temporary tables are automatically dropped at the end of a session. Existing persistent tables with the same name are not visible to the current session while the temporary table exists. Any indexes created on a temporary table are automatically temporary as well.
The LOCAL word is optional.
The name of the new table to be created. This table must not already exist. However, a temporary table can be created that has the same name as an existing permanent table.
The name of a column in the new table. Multiple column names can be specified using a comma-delimited list of column names. If column names are not provided, they are taken from the output column names of the query.
A query statement (that is, a SELECT command). Refer to SELECT for a description of the allowed syntax.
This command is functionally equivalent to SELECT INTO , but it is preferred since it is less likely to be confused with other uses of the SELECT ... INTO syntax.