Question

I have a table with two columns, ID And description. When ID = 1, the description represents the person’s name. When ID = 2, the description represents the person’s address. When ID is 3, the description represents the person’s comments.

What query must I do to select all three types of description. I tried using cases but that won’t work in my case. Union will work but I will be running my query three times. Is there a simpler and more effective way to do this?

Answer 1

I am guessing that you have some way to relate this data to a another table. If so, then you can use something like this:

select t1.someId,
    max(case when t2.id = 1 then t2.description end) name,
    max(case when t2.id = 2 then t2.description end) address,
    max(case when t2.id = 3 then t2.description end) comments
from table1 t1
left join table2 t2
    on t1.someId = t2.someid
group by t1.someId

This will give you the unique, data for each record in a specific row. You can then insert this data into another table.