Selecting from and updating the same table oracle
Selecting from and updating the same table oracle - online dating derek
A database trigger is a stored procedure that automatically executes whenever an event occurs. Oracle initiates an ‘AFTER INSERT’ trigger after an insert event has been occurred and an ‘AFTER UPDATE’ trigger after an update event has been occurred.CREATE or REPLACE TRIGGER emp_after_insert AFTER INSERT ON emp FOR EACH ROW DECLARE BEGIN insert into emp_backup values (:new.empid, :new.fname, :new.lname); DBMS_OUTPUT.
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When the subquery fails to find a matching row in tbl B, the subquery returns NULL.
But since the UPDATE has no WHERE clause, it will update all rows, even those where the subquery returns NULL.
In addition, we would want to see their zipcode, and their country code.
Let’s create a table: UPDATE customer_order_total cot SET cot.postal_code = ( SELECT c.cust_address.postal_code FROM oe.customers c WHERE c.customer_id = cot.customer_id ), cot.country_code = ( SELECT c.cust_address.country_id FROM oe.customers c WHERE c.customer_id = cot.customer_id ) ; UPDATE customer_order_total cot SET ( cot.postal_code, cot.country_code ) = ( SELECT c.cust_address.postal_code, c.cust_address.country_id FROM oe.customers c WHERE c.customer_id = cot.customer_id ) ; In the update statement above, you need to make sure that you specify the (in this case) the unique identifier in the customer table that matches the customer id in our customer_order_total table.
DECLARE rec_contract CONTRACT%ROWTYPE := Null; BEGIN -- ... -- "Set" logic UPDATE CONTRACT SET ROW = rec_contract WHERE CONTRACT_ID = rec_contract.
CONTRACT_ID; IF (SQL%ROWCOUNT = 0) THEN INSERT INTO CONTRACT VALUES rec_contract; END IF; END; logic too.
Now, recently I needed to copy a bunch of data within the same table but with a different primary key.
I started to write a bunch of code like the above, but I just needed some of code.
works fine when I try to update all the records in tbl A, however, in this case I only have missing data which I have identified and populated in tbl B.
When I try to update only the missing data the non-matched data is also updated but to NULL. The reason some of your rows are getting NULLs updated is due to the subquery.
But, the syntax example above might not show the whole truth, since we can have a situation like this: In the expanded version of our UPDATE syntax above, the value that we want to update column1 with, actually comes from a different table.