Create a table

A table can be visualized as a two-dimensional arrangement of data consisting of rows and columns.

The row is the horizontal part containing one or more columns. The column is the vertical part containing one or more rows of data of one data type. All data for a column must be of the same type. A table in SQL is a keyed or non-keyed physical file.

Tables are created using the CREATE TABLE statement. The definition must include its name and the names and attributes of its columns. The definition may include other attributes of the table such as primary key.

Example: Given that you have administrative authority, create a table named 'INVENTORY' with the following columns:

Part number: Integer between 1 and 9999, and must not be null
Description: Character of length 0 to 24
Quantity on hand: Integer between 0 and 100000

The primary key is PARTNO.

CREATE TABLE INVENTORY
                 (PARTNO         SMALLINT     NOT NULL,
                  DESCR          VARCHAR(24 ),
                  QONHAND        INT,
                  PRIMARY KEY(PARTNO))

Add and remove constraints to a table
Constraints can be added to a new table or to an existing table. You can add a unique or primary key, a referential constraint, or a check constraint, using the ADD constraint clause on the CREATE TABLE or the ALTER TABLE statements.
Referential integrity and tables
Referential integrity is the condition of a set of tables in a database in which all references from one table to another are valid.
Remove constraints
This example removes the primary key over column DEPTNO in table DEPARTMENT.
Check pending
Referential constraints and check constraints can be in a state known as check pending, where potential violations of the constraint exist.

Parent topic: Data definition language (DDL)

Related information

Data types