What is difference between trigger and constraint?

Trigger affects only those rows, which are added after it is enabled. Constraints affects all the rows i.e. the once that existed before and the ones that were newly added. A constraint is responsible only for maintaining the integrity of the database.

What is the difference between check constraints and assertions?

The difference between the two is that CHECK CONSTRAINTS are, in a sense, much “simpler” : they are rules that relate to one single row only, while ASSERTIONs can involve any number of other tables, or any number of other rows in the same table.

What are constraints and triggers?

CREATE CONSTRAINT TRIGGER creates a constraint trigger. Constraint triggers must be AFTER ROW triggers. They can be fired either at the end of the statement causing the triggering event, or at the end of the containing transaction; in the latter case they are said to be deferred.

Is trigger a constraint in SQL?

Trigger is a statement that a system executes automatically when there is any modification to the database. Triggers are used to specify certain integrity constraints and referential constraints that cannot be specified using the constraint mechanism of SQL.

What advantages do triggers have over normal table constraints?

Pros of SQL Server Triggers

• Triggers are easy to code.
• Triggers allow you to create basic auditing.
• You can call stored procedures and functions from inside a trigger.
• Triggers are useful when you need to validate inserted or updated data in batches instead of row by row.

What is an assertion example?

The definition of an assertion is an allegation or proclamation of something, often as the result of opinion as opposed to fact. An example of someone making an assertion is a person who stands up boldly in a meeting with a point in opposition to the presenter, despite having valid evidence to support his statement.

What is integrity constraints in SQL?

Integrity Constraints are the protocols that a table’s data columns must follow. These are used to restrict the types of information that can be entered into a table. This means that the data in the database is accurate and reliable. You may apply integrity Constraints at the column or table level.

How do you create a trigger?

To create a trigger in your own schema on a table in your own schema or on your own schema ( SCHEMA ), you must have the CREATE TRIGGER system privilege. To create a trigger in any schema on a table in any schema, or on another user’s schema ( schema . SCHEMA ), you must have the CREATE ANY TRIGGER system privilege.

Why you should not use triggers?

Some Good Reasons Not to Use Triggers There are some equally valid reasons to not use triggers, including: they may add workload to the database and cause the system to run slower because they are executed for every user every time the event occurs on which the trigger is created.

When to use a check or a trigger in SQL?

To make matters more confusing – a trigger could be used to enforce a check constraint and in some DBs can take the place of an assertion (by allowing you to run code un-related to the table being modified). A common mistake for beginners is to use a check constraint when a trigger is required or a trigger when a check constraint is required.

How is a constraint trigger used in SQL?

For a constraint type trigger, the idea generally is to write a query to return bad data then in the trigger test that this result is empty. You haven’t posted many details of your tables so I will guess.

Is the database trigger the same as the integrity constraint?

A database trigger is not the same as an integrity constraint. A database trigger defined to enforce an integrity rule does not check data already loaded into a table. Therefore, it is recommended that you use a trigger only when the integrity rule cannot be enforced by an integrity constraint. ORA-00001 – Unique constraint violated.

What is a check constraint in SQL Server?

Check Constraint – A check is a piece of SQL which makes sure a condition is satisfied before action can be taken on a record. In plain English this would be something like: All customers must have an account balance of at least $100 in their account. Which would look something like: