Creating tables

Use the CREATE TABLE statement to create a native table in the Vertica.

Use the CREATE TABLE statement to create a native table in the Vertica logical schema. You can specify the columns directly, as in the following example, or you can derive a table definition from another table using a LIKE or AS clause. You can specify constraints, partitioning, segmentation, and other factors. For details and restrictions, see the reference page.

The following example shows a basic table definition:

=> CREATE TABLE orders(
    orderkey    INT,
    custkey     INT,
    prodkey     ARRAY[VARCHAR(10)],
    orderprices ARRAY[DECIMAL(12,2)],
    orderdate   DATE

Table data storage

Unlike traditional databases that store data in tables, Vertica physically stores table data in projections, which are collections of table columns. Projections store data in a format that optimizes query execution. Similar to materialized views, they store result sets on disk rather than compute them each time they are used in a query.

In order to query or perform any operation on a Vertica table, the table must have one or more projections associated with it. For more information, see Projections.

Deriving a table definition from the data

You can use the INFER_TABLE_DDL function to inspect Parquet, ORC, JSON, or Avro data and produce a starting point for a table definition. This function returns a CREATE TABLE statement, which might require further editing. For columns where the function could not infer the data type, the function labels the type as unknown and emits a warning. For VARCHAR and VARBINARY columns, you might need to adjust the length. Always review the statement the function returns, but especially for tables with many columns, using this function can save time and effort.

Parquet, ORC, and Avro files include schema information, but JSON files do not. For JSON, the function inspects the raw data to produce one or more candidate table definitions. See the function reference page for JSON examples.

In the following example, the function infers a complete table definition from Parquet input, but the VARCHAR columns use the default size and might need to be adjusted:

=> SELECT INFER_TABLE_DDL('/data/people/*.parquet'
        USING PARAMETERS format = 'parquet', table_name = 'employees');
WARNING 9311:  This generated statement contains one or more varchar/varbinary columns which default to length 80
 create table "employees"(
  "employeeID" int,
  "personal" Row(
    "name" varchar,
    "address" Row(
      "street" varchar,
      "city" varchar,
      "zipcode" int
    "taxID" int
  "department" varchar
(1 row)

For Parquet files, you can use the GET_METADATA function to inspect a file and report metadata including information about columns.

See also