I'm trying to represent in a UML diagram the following:
What I'm trying to explain with the diagram is that the program will do a fetch in the table using three variables: col1val, col2val and col3val; & then it will return variable col4val.
However, this is supposed to be a hierarchical fetch (not sure about the terminology), which means that it should first look up for all the columns at the same time:
SELECT col4 FROM Table WHERE col1 = col1val AND col2 = col2val AND col3 = col3val;
If it's successful, the program should leave the section and stop fetching. However, if the program fails to do the fetch, then it will try again, but adding the condition
col1val IS NULL.
SELECT col4 FROM Table WHERE col1 IS NULL AND col2 = col2val AND col3 = col3val;
Like that as many times and fields as possible. If the program ends up finding nothing after the last iteration, we now retrieve
From the diagram, the first thing I would like to avoid is to repeat:
Because it is exactly the same in all instances. I'm only nullifying fields.
I explored the option of building an IFs "pyramid", but I need to adjust the diagram with certain frequency, so repositioning the alt/if section every time takes too much.
The following recommendations will help you in your SQL tuning process.
You'll find 3 sections below:
ALTER TABLE `Table` ADD INDEX `table_idx_col1_col1v_col2_col2v_col3_col3v` (`col1`,`col1val`,`col2`,`col2val`,`col3`,`col3val`);
SELECT Table.col4 FROM Table WHERE Table.col1 = Table.col1val AND Table.col2 = Table.col2val AND Table.col3 = Table.col3val