Updating inside an oracle function

22-Dec-2019 00:13 by 10 Comments

Updating inside an oracle function - fuckbookdating contacts

Oracle’s MERGE statement is tailor-made for situations when you want to do an "upsert" i.e.update existing rows in a table or insert new rows depending on a match condition.

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, and before you increment it, you need to get its current value.

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The functionality supports the following use case: page after an unsuccessful attempt to save.

Consider another table STUDENT_N, which holds updates for the target table STUDENT.

Every week, table STUDENT needs to be synchronized with the data in STUDENT_N – any new entries for students who attempted the GMAT to be inserted, plus corrections if any made to the existing details.

Transaction and SELECT FOR UPDATE To resolve this issue we can start a transaction and you SELECT FOR UPDATE in My SQL: Now if a transaction executes SELECT FOR UPDATE, all other concurrent transactions will be blocked on execution of their SELECT FOR UPDATE until the first transaction issues a COMMIT, or lock time-out expires.

Using transactions to increment counters is reliable but not perfect solution since locks can decrease the overall performance.

I want to test on a level playing field and remove special factors that unfairly favour one method, so there are some rules: TEST (Update Source) - 100K rows TEST (Update target) - 10M rows Name Type Name Type ------------------------------ ------------ ------------------------------ ------------ PK NUMBER PK NUMBER FK NUMBER FK NUMBER FILL VARCHAR2(40) FILL VARCHAR2(40) Not many people code this way, but there are some Pro*C programmers out there who are used to Explicit Cursor Loops (OPEN, FETCH and CLOSE commands) and translate these techniques directly to PL/SQL.

The UPDATE portion of the code works in an identical fashion to the Implicit Cursor Loop, so this is not really a separate "UPDATE" method as such.

Fortunately, there is another option that does not require using transactions, and can select and update the counter with a single access to the table: Session and Procedure Variables This statement selects the current value of the counter and increments it in a single statement: , and use it after the UPDATE statement (you do not need to execute SELECT @cur_value).

LAST_INSERT_ID Function Instead of using a session or local variable, you can get the same functionality using LAST_INSERT_ID function.

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