Sunday, December 19, 2010
- It's a field in a domain it helps in domain level data validation.
- In some cases when we define a domain that all the table fields or structure components referring to this domain should be checked against a certain table. This information can be stored in the domain by entering a value table.
- Entering a value table does not implement a check. The check against the value table only takes place when a foreign key is defined.
- It helps in field level data validation.
- A foreign key links two tables T1 and T2 by assigning fields of table T1 to the primary key fields of table T2. Table T1 is called the foreign key table (dependent table) and table T2 the check table (referenced table).
- When an entry is made in the check field, there is a check whether the check table contains a record with the key defined by the values in the foreign key fields. If this is so, the entry is valid. Otherwise the system rejects the entry.
0 comments:
Post a Comment
Your useful comments, suggestions are appreciated.Your comments are moderated.