This page covers some fundamental basics for using SQL in Polypheny.
Identifiers
In SQL, an identifier is a name given to a database object. Identifiers in Polypheny must adhere to the following rules:
- Naming: Identifiers should start with a letter and can only contain letters, digits, and underscores.
- Case Sensitivity: Case sensitivity depends on the namespace. The default is not case-sensitive. For instance,
employeeandEmployeewould refer to the same object. - Reserved Keywords: If an identifier name clashes with a reserved keyword, the name needs to be quoted. Quoted identifiers, such as
"user", start and end with double quotes.
Operator and Function Names
In Polypheny, operator and function names are always case-insensitive. This means that SELECT, select, SeLect, and so on, are treated as the same.
Strings
Strings in Polypheny are enclosed within single quotes ('). If you need to use a single quote within a string, it must be escaped by doubling it. For example,
INSERT INTO test VALUES (1, 'A single quote '' needs to be doubled')
will insert the string:
A single quote ' needs to be doubled
Accessing Entities from Different Namespaces
You can access entities (like tables or views) from a different namespace by prefixing the identifier with the namespace name, separated by a dot. For example, if there’s a table employee in namespace hr, you could refer to it as hr.employee.
Queries without a table
In Polypheny, SELECT queries do not require a FROM clause. This is contrary to standard SQL where a FROM clause is typically mandatory. In such cases, Polypheny would return a pseudo table with a single row.
For example, the following is a valid query in Polypheny:
SELECT 42;
This would return a pseudo table with a single row and a single column containing the value 42.
