Home
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.
Data types and expressionsThese topics describe the data types and expressions that HCL OneDB™supports.
Expression
CAST ExpressionsUse the CAST (... AS ...) keywords or the double-colon ( :: ) cast operator to convert the data type of the value of an expression to some other target data type.
The Keyword NULL in Cast Expressions

The Keyword NULL in Cast Expressions

Cast expressions can appear in the projection list, including expressions of the form NULL::datatype, where datatype is any data type known to the database:

SELECT newtable.col0, null::int FROM newtable;

The keyword NULL has a global scope of reference within expressions. In SQL, the keyword NULL is the only syntactic mechanism for accessing a NULL value. Any attempt to redefine or restrict the global scope of the keyword NULL (for example, declaring an SPL variable called null) disables any cast expression that involves a NULL value. Make sure that the keyword NULL receives its global scope in all expression contexts.