Selecting from and updating the same table oracle
Why not to use SELECT statement to get the current value and then UPDATE to update the counter: The problem with this query is that concurrent sessions can execute SELECT at the same time and get the same current value.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.Execution of a table function can be parallelized, and returned rows can be streamed directly to the next process without intermediate staging.Rows from a collection returned by a table function can also be —that is, iteratively returned as they are produced instead of in a batch after all processing of the table function's input is completed.LAST_INSERT_ID Function Instead of using a session or local variable, you can get the same functionality using LAST_INSERT_ID function.LAST_INSERT_ID is typically used to get the latest value inserted into a AUTO_INCREMENT column, but it also has another feature.
First, one set of slave processes partitions the data as directed in the function's declaration; then a second set of slave scans executes the table function in parallel on the partitioned data.
This makes it possible to use a table function like a virtual table.
Pipelined table functions can be implemented in two ways: The interface approach requires you to implement a set of well-defined interfaces in a procedural language.
Pipelined table functions are used in SQL statements in exactly the same way regardless of the approach used to implement them. This keyword indicates that the function will return rows iteratively.
The return type of the pipelined table function must be a collection type (a nested table or a varray).
The type is associated with the table function when the table function is created.