Constraints help to ensure that the data entered in the table
is correct and provide information to Sybase IQ that boosts performance.
The CREATE TABLE statement and ALTER
TABLE statement can specify many different attributes
for a table. Along with the basic table structure (number, name
and data type of columns, name and location of the table), you can specify
other features that allow control over data integrity.
Warning! Altering or creating tables could adversely interfere
with other users of the database. For large tables, ALTER
TABLE or CREATE TABLE can be a time-consuming
operation. CREATE TABLE processing delays execution
of other IQ processes until the statement completes. Although you
can execute ALTER TABLE statements while other
connections are active, you cannot execute them if any other connection
is using the table to be altered. During ALTER TABLE,
no other requests referencing the table being altered are allowed while
the statement is being processed.