Unit 21: Domain Integrity Constraints

Decent Essays

Unit 21 – M2
A - Explain domain integrity constraints
1. Domain integrity constraints in general
Domain integrity helps database developers determine what values are valid for a particular column. The way that this process is enforced is by using standard procedures and rules during the database design phase. A domain definition can be used instead of data types in a column definition. This has the advantage that the same definition off data type, check ‘clauses’ and ‘default’ values can be used in many column definition and therefore those columns are guaranteed to have the same attributes. When functions are performed on the data the functions must ensure integrity. Examples of function are transforming the data, storing the history, …show more content…

2. List-type constraints (lookups from your Unit 18-P4), what is their use, what effect do they have on a database (include a screenshot of a lookup from your own database)
• Check constraint
A check constraint is a rule the identifies acceptable column values for data in a row within a SQL server table. Checks constraints help enforce domain integrity. Domain integrity produces an error message and the entire insert or updates operation will fail.
Foreign key constraint
Foreign key constraints can be used to define required relationships between and with tables. When a foreign key constraint is added to an existing column or columns in the tables SQL server, by default the process will check the existing data in the column to ensure that all values, except NULL, exist in the column(s) of the referenced primary key or unique constraint.
• Not null constraint
A not-null constraint is a restriction placed on a column in a relational database table. It enforces the condition that, in that column, every row of the data must contain a value – it cannot be left blank during insert or updates operation will fail.

3. Format-type constraints, what is their use, what effect do they have on the database (include a screenshot of a lookup from your own database)
From this screenshot below, we are able to understand that user can encounter the issue of formatting

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