Contents
How does a trigger work in SQL Server?
Triggers are like procedures that are implicitly executed when an INSERT, DELETE, UPDATE statement is fired on a table whether by a SQL statement or by a user-defined procedure.
What is the difference between old and new triggers in Oracle?
For the row that the trigger is processing: For an INSERT trigger, OLD contains no values, and NEW contains the new values. For an UPDATE trigger, OLD contains the old values, and NEW contains the new values. For a DELETE trigger, OLD contains the old values, and NEW contains no values.
What happens when a trigger is disabled in Oracle?
Note that if a trigger is disabled, it is not fired when the triggering event occurs. By default, if you don’t specify the clause ENABLE / DISABLE , the trigger is created with the enabled state. For each triggering event e.g., INSERT, UPDATE, or DELETE, you can define multiple triggers to fire.
Is the create keyword optional in Oracle trigger?
The CREATE keyword specifies that you are creating a new trigger. The OR REPLACE keywords are optional. They are used to modify an existing trigger. Even though the OR REPLACE keywords are optional, they appear with the CREATE keyword in most cases.
Now the trigger will check for the existence of the temporary table and if the temporary table exists the trigger will return and not execute the code, else it will execute its code as normal. To see how it works, run the following statements to create a table and a trigger.
How to execute a long running SQL query?
Instead of holding execution on a long running statement (s), it allows you to carry on to next line of code. In this post, we will implement this functionality to get execute Sql query asynchronously. In our sample project which is a WPF application, we will use Callback mechanism.
Can a long running query be a disastrous event?
In some occasions, a long running query could be a catalyst to a disastrous event. If you care about your database, optimizing query performance and detecting long running queries must be performed regularly. Things do get harder though when multiple instances in a group or cluster are involved.
Why does sqlreader ignore long running SQL query?
SqlReader’s Close or Read is designed to ignore this Cancel () call if this call is not placed before them and so on. It is a great programming style that solves many issues and help you to build more interactive UI based applications. Instead of holding execution on a long running statement (s), it allows you to carry on to next line of code.
Why does INSERT statement not fire the trigger?
You will notice that the INSERT statement did not fire the trigger and since the temporary table that was created is local to the session the trigger cannot be bypassed by any of the other sessions. This works fine, but having to use the Tempdb database to create a temp table and then drop the temp table causes overhead which can be avoided. Using
What’s the best way to disable a trigger?
Disabling a trigger is something that you may need to do at certain times especially when performing admin tasks on a table. The best way to accomplish this is to use the following command to completely disable a trigger. The trigger once disabled will not fire until it is enabled again. To enable the trigger you use the following code:
When to set context info in SQL trigger?
Before issuing the INSERT statement, the context info is set to a value. In the trigger, we are first checking if the value of context info is the same as the value declared.
How to prevent a trigger from being executed?
If you want to prevent the trigger from being executed you can do the following: Before issuing the INSERT statement, the context info is set to a value. In the trigger, we are first checking if the value of context info is the same as the value declared.
How to prevent mutually recursive execution of triggers?
For example: Note that trigger_nestlevel () appears to be 1-based, not 0-based. If you want each of the two triggers to execute once, but not more often, just check for trigger_nestlevel () < 3 in both triggers. I’m not sure about doing it per transaction, but do you need nested triggers switched on for other parts?