Sybase 12.4.2 사용자 설명서

CHAPTER 7    Ensuring Data Integrity

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You can replace a CHECK condition on a column in the same way as you 
would add a CHECK condition. The following statement adds or replaces 
an unenforced CHECK condition on the 

phone

 column of the 

customer

 

table:

ALTER TABLE customer

MODIFY phone

CHECK ( phone LIKE ’___-___-____’ )

UNENFORCED

There are two ways of modifying a CHECK condition defined on the table, as 
opposed to a CHECK condition defined on a column.

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You can add a new CHECK condition using ALTER TABLE with an ADD 
table-constraint clause.

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You can delete all existing CHECK conditions, including column CHECK 
conditions, using ALTER TABLE DELETE CHECK, and then add in new 
CHECK conditions.

All CHECK conditions on a table, including CHECK conditions on all its 
columns and CHECK conditions inherited from user-defined data types, are 
removed using the ALTER TABLE statement with the DELETE CHECK 
clause, as follows:

ALTER TABLE table_name

DELETE CHECK

Deleting a column from a table does not delete CHECK conditions associated 
with the column that are held in the table constraint. If the constraints are not 
removed, any attempt to query data in the table will produce a column not 
found error message.

The relational structure of the database enables the database server to identify 
information within the database. Adaptive Server IQ also ensures that primary 
key-foreign key relationships between tables are properly upheld by all the 
rows in any join index relying on these relationships.