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SQL triggers are powerful tools that can immensely simplify the process of maintaining data consistency in Databricks. Trigger in SQL is a stored procedure that is run automatically when a certain event occurs. This can involve the modification of a table or even a record within the database.
Creating a Basic SQL Trigger
Here’s an example of how to make a simple trigger in SQL. In this example, we’re making a trigger ‘tr_fruitsUpdate’ that automatically logs an update to our ‘fruits’ table:
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CREATE TRIGGER tr_fruitsUpdate ON fruits AFTER UPDATE AS BEGIN INSERT INTO fruits_log SELECT GETDATE(), 'update', * FROM deleted END |
This code will create a new row in the ‘fruits_log’ table every time a row in the ‘fruits’ table is updated, enabling for easier tracking of data changes.
Triggering Multiple Actions
SQL triggers can perform multiple actions following the initial triggering event. For example, here’s how you could make another update in a separate table following the first update:
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CREATE TRIGGER tr_fruitsUpdate ON fruits AFTER UPDATE AS BEGIN INSERT INTO fruits_log SELECT GETDATE(), 'update', * FROM deleted UPDATE statistics SET fruit_count = (SELECT COUNT(*) FROM fruits) WHERE stat_name = 'Total Fruits' END |
This will not only log the update, but also update a ‘Total Fruits’ record in a ‘statistics’ table.
Creating a Trigger with a Conditional Statement
Triggers can also use conditional statements. Here’s how to create a trigger that only activates if the updated price is above a certain threshold:
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CREATE TRIGGER tr_expensiveFruitInsert ON fruits AFTER INSERT AS BEGIN IF (SELECT price FROM inserted) > 100 BEGIN INSERT INTO expensive_fruits SELECT * FROM inserted END END |
SQL triggers are immensely customizable and users can define exactly when and how they should operate. This ensures that they only activate when necessary, optimizing performance.
Conclusion
In conclusion, SQL triggers offer an automatic and efficient way to ensure data consistency within your Databricks database. Whether you are logging changes, updating records, or guarding against undesirable data, triggers can assist immensely.