Replicating a table

You can create a table from an existing one using CREATE TABLE with the LIKE clause:.

You can create a table from an existing one using CREATE TABLE with the LIKE clause:

CREATE TABLE [ IF NOT EXISTS ] [[ { namespace. | database. } ]schema.]table
LIKE [[ { namespace. | database. } ]schema.]existing-table
  [ { INCLUDING | EXCLUDING } PROJECTIONS ]
  [ { INCLUDE | EXCLUDE } [SCHEMA] PRIVILEGES ]

Creating a table with LIKE replicates the source table definition and any storage policy associated with it. Table data and expressions on columns are not copied to the new table.

The user performing the operation owns the new table.

The source table cannot have out-of-date projections and cannot be a temporary table.

Copying constraints

CREATE TABLE LIKE copies all table constraints except for:

  • Foreign key constraints.
  • Sequence column constraints.

For any column that obtains its values from a sequence, including IDENTITY columns, Vertica copies the column values into the new table, but removes the original constraint. For example, the following table definition sets an IDENTITY constraint on the ID column:

=> CREATE TABLE public.Premium_Customer
  (
    ID IDENTITY,
    lname varchar(25),
    fname varchar(25),
    store_membership_card int
  );

The following CREATE TABLE LIKE statement uses the source table Premium_Customer to create the replica All_Customers. Vertica removes the IDENTITY constraint, changing the column to an integer column with a NOT NULL constraint:

=> CREATE TABLE All_Customers LIKE Premium_Customer;
   CREATE TABLE

=> SELECT export_tables('','All_Customers');
                   export_tables
---------------------------------------------------
CREATE TABLE public.All_Customers
(
    ID int NOT NULL,
    lname varchar(25),
    fname varchar(25),
    store_membership_card int
);
(1 row)

Including projections

You can qualify the LIKE clause with INCLUDING PROJECTIONS or EXCLUDING PROJECTIONS, which specify whether to copy projections from the source table:

  • EXCLUDING PROJECTIONS (default): Do not copy projections from the source table.

  • INCLUDING PROJECTIONS: Copy current projections from the source table. Vertica names the new projections according to Vertica naming conventions, to avoid name conflicts with existing objects.

Including schema privileges

You can specify default inheritance of schema privileges for the new table:

  • EXCLUDE [SCHEMA] PRIVILEGES (default) disables inheritance of privileges from the schema

  • INCLUDE [SCHEMA] PRIVILEGES grants the table the same privileges granted to its schema

For more information see Setting privilege inheritance on tables and views.

Examples

  1. Create the table states:

    => CREATE TABLE states (
     state char(2) NOT NULL, bird varchar(20), tree varchar (20), tax float, stateDate char (20))
     PARTITION BY state;

  2. Populate the table with data:

    INSERT INTO states VALUES ('MA', 'chickadee', 'american_elm', 5.675, '07-04-1620');
INSERT INTO states VALUES ('VT', 'Hermit_Thrasher', 'Sugar_Maple', 6.0, '07-04-1610');
INSERT INTO states VALUES ('NH', 'Purple_Finch', 'White_Birch', 0, '07-04-1615');
INSERT INTO states VALUES ('ME', 'Black_Cap_Chickadee', 'Pine_Tree', 5, '07-04-1615');
INSERT INTO states VALUES ('CT', 'American_Robin', 'White_Oak', 6.35, '07-04-1618');
INSERT INTO states VALUES ('RI', 'Rhode_Island_Red', 'Red_Maple', 5, '07-04-1619');

  3. View the table contents:

    => SELECT * FROM states;
 state |        bird         |     tree     |  tax  |      stateDate
-------+---------------------+--------------+-------+----------------------
 VT    | Hermit_Thrasher     | Sugar_Maple  |     6 | 07-04-1610
 CT    | American_Robin      | White_Oak    |  6.35 | 07-04-1618
 RI    | Rhode_Island_Red    | Red_Maple    |     5 | 07-04-1619
 MA    | chickadee           | american_elm | 5.675 | 07-04-1620
 NH    | Purple_Finch        | White_Birch  |     0 | 07-04-1615
 ME    | Black_Cap_Chickadee | Pine_Tree    |     5 | 07-04-1615
(6 rows

  4. Create a sample projection and refresh:

    => CREATE PROJECTION states_p AS SELECT state FROM states;

=> SELECT START_REFRESH();

  5. Create a table like the states table and include its projections:

    => CREATE TABLE newstates LIKE states INCLUDING PROJECTIONS;

  6. View projections for the two tables. Vertica has copied projections from states to newstates:

    => \dj
                                                      List of projections
            Schema             |                   Name                    |  Owner  |       Node       | Comment
-------------------------------+-------------------------------------------+---------+------------------+---------
 public                        | newstates_b0                              | dbadmin |                  |
 public                        | newstates_b1                              | dbadmin |                  |
 public                        | newstates_p_b0                            | dbadmin |                  |
 public                        | newstates_p_b1                            | dbadmin |                  |
 public                        | states_b0                                 | dbadmin |                  |
 public                        | states_b1                                 | dbadmin |                  |
 public                        | states_p_b0                               | dbadmin |                  |
 public                        | states_p_b1                               | dbadmin |                  |

  7. Query the new table:

    => SELECT * FROM newstates;
 state | bird | tree | tax | stateDate
-------+------+------+-----+-----------
(0 rows)

When you use the CREATE TABLE LIKE statement, storage policy objects associated with the table are also copied. Data added to the new table use the same labeled storage location as the source table, unless you change the storage policy. For more information, see Working With Storage Locations.

See also