在单个查询中从多个表中查找数据

Question

I'm working in postgreSQL and my proble is this: I have 3 tables with a different ID serialized. For example, if I insert a row in the table 1, the id will be '00001', if I insert a row in the table 3. the id will be '00002'....

So, i'm trying to create a query that gets the data with from the three tables using a single query. I don't know if is necessary create a function plpgsql or just with a simple query, I did not make it yet.

I want something like this: (But in postgreSQL)

function getData(ID){
  if( ID exists in table 1){
    return select * from table 1
  }
  if( ID exists in table 2){
    return select * from table 1
  }
  if( ID exists in table 3){
    return select * from table 3
  }
}

But of course, this code is in another language and wrong, a pseudocode.

Any suggestion?

Answer 1

Why not just use union all ?

select t1.* from table1 t1 where t1.id = 1
union all
select t2.* from table2 t2 where t2.id = 1
union all
select t3.* from table3 t3 where t3.id = 1