Tables, Creating

You create a new table in a database by issuing a CREATE TABLE statement. The syntax varies widely among vendors, but the following subsections show reasonable examples for each platform. Bear in mind the following points:

  • At a minimum, all you need is a list of column names and their datatypes:

    CREATE TABLE simple_example (
       id NUMERIC,
       name VARCHAR(15),
       last_changed DATE
    );
  • The examples give explicit names for many of the constraints, which I consider a best practice, but the CONSTRAINT constraint_name syntax is optional and is often omitted (especially on column constraints such as the NOT NULL constraint).

  • You can usually declare constraints that involve a single column as part of that column’s definition. Multi-column constraints must be declared as table-level elements. The examples demonstrate both approaches.

See the "Datatypes" section, earlier in this book, for a list of valid datatypes by platform.

Creating a Table (Oracle)

The following is a typical CREATE TABLE statement for Oracle:

CREATE TABLE oracle_example ( id NUMBER(6), name VARCHAR2(15) NOT NULL, country VARCHAR2(2) DEFAULT 'CA' CONSTRAINT country_not_null NOT NULL CONSTRAINT country_check CHECK (country IN ('CA','US')), indexed_name VARCHAR2(15), CONSTRAINT oracle_example_pk PRIMARY KEY (id), CONSTRAINT oracle_example_fk01 FOREIGN KEY (name, country) REFERENCES parent_example (name, country), CONSTRAINT oracle_example_u01 UNIQUE (name, country), CONSTRAINT oracle_example_index_upper CHECK (indexed_name ...

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