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SQL programmingYou can use the HCL OneDB™ implementation of the SQL language to develop applications for HCL OneDB™ database servers.
Guide to SQL: SyntaxThe HCL OneDB™ Guide to SQL: Syntax describes the syntax of the statements, data types, expressions, operators, and built-in functions of the HCL OneDB™ dialect of the SQL language.
SQL statementsThis chapter describes the syntax and semantics of SQL statements that are recognized by HCL OneDB™.
CREATE TABLE statementUse the CREATE TABLE statement to create a new permanent table in the current database.
Column definitionUse the column definition segment of the CREATE TABLE statement to declare the name and data type (and optionally the default value and the constraints or the security label) of a single column of the new table.
Single-Column Constraint FormatUse the Single-Column Constraint format to define and declare the name of at least one constraint on a single column, and to specify the mode of each constraint.
REFERENCES Clause

REFERENCES Clause

Use the REFERENCES clause to establish a referential relationship:

Within a table (that is, between two columns of the same table)
Between two tables (in other words, create a foreign key)

This syntax fragment is part of the Single-Column Constraint Format and the Multiple-Column Constraint Format.

REFERENCES Clause

Notes:

¹ HCL OneDB™ extension


Element	Description	Restrictions	Syntax
column	A referenced column	See Restrictions on Referential Constraints.	Identifier
table	The referenced table	Must reside in the same database as the referencing table	Identifier

The referencing column (the column being defined) is the column or set of columns that refers to the referenced column or set of columns. The referencing column can contain NULL and duplicate values, but values in the referenced column (or set of columns) must be unique.

The relationship between referenced and referencing columns is called a parent-child relationship, where the parent is the referenced column (primary key) and the child is the referencing column (foreign key). The referential constraint establishes this parent-child relationship.

When you create a referential constraint, the database server automatically creates an internal index on the constrained column or columns.