Sybase IQ features

The following Sybase IQ features are not found in many other SQL implementations.

Sybase IQ has date, time, and timestamp types that include year, month and day, hour, minutes, seconds and fraction of a second. For insertions or updates to date fields, or comparisons with date fields, a free format date is supported.

In addition, the following operations are allowed on dates:

Adaptive Server IQ supports both entity and referential integrity. This has been implemented via the following two extensions to the CREATE TABLE and ALTER TABLE commands.

PRIMARY KEY ( column-name, ... )
[NOT NULL] FOREIGN KEY [role-name] 
				[(column-name, ...)]
			REFERENCES table-name [(column-name, ...)]
				[ CHECK ON COMMIT ]

The PRIMARY KEY clause declares the primary key for the relation. Adaptive Server IQ will then enforce the uniqueness of the primary key, and ensure that no column in the primary key contains the NULL value.

The FOREIGN KEY clause defines a relationship between this table and another table. This relationship is represented by a column (or columns) in this table which must contain values in the primary key of another table. The system will then ensure referential integrity for these columns - whenever these columns are modified or a row is inserted into this table, these columns will be checked to ensure that either one or more is NULL or the values match the corresponding columns for some row in the primary key of the other table. For more information, see CREATE TABLE statement.

Sybase IQ allows automatic joins between tables. In addition to the NATURAL and OUTER join operators supported in other implementations, Sybase IQ allows KEY joins between tables based on foreign-key relationships. This reduces the complexity of the WHERE clause when performing joins.

Adaptive Server IQ allows more than one table to be referenced by the UPDATE command. Views defined on more than one table can also be updated. Many SQL implementations will not allow updates on joined tables.

The ALTER TABLE command has been extended. In addition to changes for entity and referential integrity, the following types of alterations are allowed:

ADD column data-type
MODIFY column data-type
DELETE column
RENAME new-table-name
RENAME old-column TO new-column

The MODIFY can be used to change the maximum length of a character column as well as converting from one data type to another. For more information, see ALTER TABLE statement.

Unlike Adaptive Server Anywhere, Sybase IQ does not allow subqueries to appear wherever expressions are allowed. Sybase IQ supports subqueries only as allowed in the SQL-1989 grammar, plus in the SELECT list of the top level query block or in the SET clause of an UPDATE statement. It does not support Adaptive Server Anywhere's extensions.

Many SQL implementations only allow subqueries on the right side of a comparison operator. For example, the following command is valid in Adaptive Server IQ but not valid in most other SQL implementations.

SELECT		emp_lname,
			emp_birthdate,
			(	SELECT skill 
				FROM department
				WHERE emp_id = employee.emp_ID
				AND dept_id = 200 )
FROM employee

When using Embedded SQL, cursor positions can be moved arbitrarily on the FETCH statement. Cursors can be moved forward or backward relative to the current position or a given number of records from the beginning or end of the cursor.