Can we use SELECT statement in trigger MySQL?
You can declare local variables in MySQL triggers, with the DECLARE syntax. When you assign a value to a variable, you must ensure that the query returns only a single value, not a set of rows or a set of columns.
Can we use SELECT statement in trigger?
The trigger event that initiates the trigger action can be an INSERT, DELETE, UPDATE, or a SELECT statement.
How do I use triggers in MySQL?
Create Trigger in MySQL
- First, specify the name of the trigger that you want to create after the CREATE TRIGGER keywords.
- Next, specify the trigger action time which can be either BEFORE or AFTER which indicates that the trigger is invoked before or after each row is modified.
Can a trigger be fired on SELECT statement?
No there is no provision of having trigger on SELECT operation. You can use stored procedure which takes parameters that are fetched from SELECT query and call this procedure after desired SELECT query.
Can I call a trigger directly called from an application?
Unlike a subprogram, a trigger cannot be invoked directly. A trigger is invoked only by its triggering event, which can be caused by any user or application. You might be unaware that a trigger is executing unless it causes an error that is not handled properly.
How many tables can a trigger associate to in MySQL?
MySQL triggers fire depending on the activation time and the event for a total of six unique trigger combinations.
Can trigger accept parameters?
Basically you cannot pass parameters to a Trigger because Triggers get fired automatically by the database engine, and you do not interact with them directly as they execute. Putting it in another way, Stored Procedures and Functions etc.
What is trigger syntax in MySQL?
Its syntax is as follows − CREATE TRIGGER trigger_name trigger_time trigger_event ON table_name FOR EACH ROW BEGIN END; Here, Trigger_name is the name of the trigger which must be put after the CREATE TRIGGER statement.
Where are triggers stored in MySQL?
Where are triggers stored? Triggers are stored in the mysql. triggers system table, which is part of the data dictionary.
How many times trigger statement executed?
If you are doing 5 updates that update 1 row, the trigger will be executed 5 times. Show activity on this post. Considering you are using SQL Server, the trigger will only fire once every Update. If this is not what you want, you could consider using different update statements to make sure the trigger fires everytime.
How many times trigger will be executed?
Statement level triggers executes only once for each single transaction. Specifically used for data auditing purpose.