Merge, Update, or Insert?

Question

Hey all,
I am new to using Oracle and SQL database codes in general. I am wondering what kind of statement to use for the problem I am about to explain. I will probably have coding questions down the road, which I will post in the correct part of the forum, but I thought that posting this general question would be appropriate in this forum.
My problem:
I have a TMP table which contains specific columns that were taken from the source. (Source had 85 columns, this TMP table has around 20). So, now I need to insert the data from the TMP table to different table. For example, the temp table is called TMP_SUPP_MASTER. The table we are moving this information into is TBL_SUPP_MASTER. In the TMP table there are columns like ADR_ST_LN_1, ADR_ST_LN_2, ADR_ST_LN_3, ADR_ST_LN_4...but in the TBL there is just ADDR_ST. Therefore, I need to combine those 4 columns into 1.
That was one part of the problem, another part involves inserting a single value into every row under the ORG_ID column name. The ORG_ID is not part of TMP, but is in TBL.
The last part of the problem is we have a lot of SUPP_CD (supplier codes), which are the primary keys. Well the code is built to include a facility ID followed by a "root" supplier code. Each facility ID and "root" supplier code is unique, so we are keeping those codes, but also making a column that has just the "root" supplier code. There are multiple "root" supplier codes that match up, so we are creating a parent/child relationship with those codes and having a column that marks them as 'P' or 'C'. P = parent, C = child. So I need to also insert that.
On top of all that, we will have new information coming in that needs to be updated to the table (so I'm assuming it's a merge).
Can anyone point me in the right direction to figure out this problem? I would really appreciate it. I don't need any codes, but just a simple opinion.
Thank you all!

Answer 1

991769 wrote:
Can anyone point me in the right direction to figure out this problem? I would really appreciate it. I don't need any codes, but just a simple opinion.Well, coffee is good for figuring out problems... ;-)
Performance is determined by the size of a workload and how fast it can be moved. The biggest chunk of most database workloads is I/O. I/O workloads are also slow to move.
So the basic principal for performance is to do the least amount of I/O as possible.
If you have an UPDATE using table TMP for getting the new values to update table PROD1, and you have an INSERT using table TMP for getting new data into table PROD2, this means 2 I/O workloads on TMP.
If both workloads read the entire TMP table, they are pretty much identical and results in a double workload for the same data. In this case a MERGE hitting TMP once, and then feeding updates to PROD1 and inserts to PROD2, will be a far smaller and far more effective workload.
So when tackling a problem with SQL, try and keep the I/O to only that what is necessary to achieve the goal - and guard against hitting the same rows of data with multiple passes.