How to Create a Sequence and Function in Oracle to Populate Batch Numbers for Repetitive Sequences

Sequence and Function in Oracle to Populate Batch Number

In this article, we will explore how to create a sequence and function in Oracle to populate batch numbers for repetitive sequences. This is particularly useful when performing batch loads or inserting data into a database table.

Understanding Sequences

A sequence in Oracle is an object that generates a sequence of numbers, starting from the START WITH value specified by the user. The sequence can be used to generate unique IDs, such as primary keys for tables, or to populate columns with incrementing values.

Here’s an example of creating a simple sequence:

CREATE SEQUENCE batch_seq
  START WITH 1
  MAXVALUE 999999999999999999999999999
  MINVALUE 1
  NOCYCLE
  CACHE 20
  NOORDER;

In this example, the batch_seq sequence starts with a value of 1 and can generate numbers up to a maximum value of 999999999999999999999999999. The CACHE option specifies how many values are cached in memory before they need to be recalculated. In this case, 20 values are cached.

Understanding Functions

A function in Oracle is an object that performs a specific task or calculation and returns a value. Functions can be used to perform complex calculations, validate data, or retrieve data from other tables.

Here’s an example of creating a simple function:

CREATE OR REPLACE FUNCTION get_batch_seq RETURN number AS l_return number;
BEGIN 
  SELECT batch_seq.nextval INTO l_return FROM dual;
  return l_return;
END;

In this example, the get_batch_seq function calls the batch_seq.nextval method to generate the next value in the sequence and returns it as a result.

Populating Batch Number Column

Now that we have created our sequence and function, let’s discuss how to populate a batch number column using these objects.

To populate the batch number column with incremental values from the sequence, we can use the following SQL statement:

SELECT get_batch_seq INTO l_batch_seq FROM dual;

This statement calls the get_batch_seq function to generate the next value in the sequence and stores it in a variable called l_batch_seq.

Next, we can insert data into our table with the batch number column populated using the following SQL statement:

INSERT INTO my_table (Id, First_Name, Last_Name, Run_Id)
VALUES (1, 'Alice', 'Spears', l_batch_seq);

In this example, we are inserting a new row into our my_table table with an Id value of 1 and a batch number value retrieved from the l_batch_seq variable.

Creating a Trigger

To populate the batch number column for each insertion, we can create a trigger on our table. A trigger is an object that automatically executes when certain events occur in our database.

Here’s an example of creating a trigger:

CREATE TRIGGER get_batch_seq_trigger
BEFORE INSERT ON my_table
FOR EACH ROW
BEGIN 
  SELECT get_batch_seq INTO :NEW.Run_Id FROM dual;
END;

In this example, the get_batch_seq_trigger trigger is created to execute before any insertions into our my_table table. For each row being inserted, the function get_batch_seq is called to generate the batch number value and stores it in the Run_Id column.

Conclusion

In this article, we explored how to create a sequence and function in Oracle to populate batch numbers for repetitive sequences. We created our own sequence and function using SQL statements and then populated data into a table with these values. Finally, we created a trigger to automatically execute before insertions into the table.

References

Last modified on 2024-07-04