![]() Let’s create a new table called leads to store all business leads of the company. The following table illustrates the rules.: Action The OLD and NEW references are available depending on the event that causes the trigger to be fired. You can access the data of the row being inserted, deleted, or updated using the OLD and NEW references in the form: OLD.column_name and NEW.column_name. However, if the trigger references other tables, the trigger is not removed or changed if other tables are removed or updated.įor example, a trigger references to a table named people, you drop the people table or rename it, you need to manually change the definition of the trigger. Notice that if you drop a table, all associated triggers are also deleted. In case you omit the WHEN clause, the trigger is executed for all rows. If you use a condition in the WHEN clause, the trigger is only invoked when the condition is true. It has not yet supported the FOR EACH STATEMENT triggers. If the trigger associated with the table is fired one time, we call this trigger a FOR EACH STATEMENT trigger.Īs of version 3.9.2, SQLite only supports FOR EACH ROW triggers. This trigger is called FOR EACH ROW trigger. Suppose you use a UPDATE statement to update 10 rows in a table, the trigger that associated with the table is fired 10 times. If you combine the time when the trigger is fired and the event that causes the trigger to be fired, you have a total of 9 possibilities: Finally, place the trigger logic in the BEGIN END block, which can be any valid SQL statements.After that, indicate the table to which the trigger belongs.Then, specify the event that causes the trigger to be invoked such as INSERT, UPDATE, or DELETE.However, you can only create an INSTEAD OF trigger on a view. You can create BEFORE and AFTER triggers on a table. Next, determine when the trigger is fired such as BEFORE, AFTER, or INSTEAD OF.First, specify the name of the trigger after the CREATE TRIGGER keywords.ĮND Code language: SQL (Structured Query Language) ( sql ) To create a new trigger in SQLite, you use the CREATE TRIGGER statement as follows: CREATE TRIGGER trigger_name In addition, you use triggers to enforce complex business rules centrally at the database level and prevent invalid transactions. For example, you want to log the changes in the sensitive data such as salary and address whenever it changes. You often use triggers to enable sophisticated auditing. What is an SQLite triggerĪn SQLite trigger is a named database object that is executed automatically when an INSERT, UPDATE or DELETE statement is issued against the associated table. Summary: this tutorial discusses SQLite trigger, which is a database object fired automatically when the data in a table is changed.
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