Joining multiple unrelated tables in MySQL

Question

I have a site that stores `<select>` options in a number of tables, and extracts all of the relevant ones depending on the individual page. At the moment, I wind up with a query like this: `SELECT foo FROM foo_tbl;SELECT bar FROM bar_tbl;etc`. It's not really a bad problem, but I have to iterate over each select result individually. I'd like to extract all of them into a single grid, then do something like ``` if $row['foo'] != NULL { add to the foo options } if $row['bar'] != NULL { add to the bar options } etc ``` If I use a query like `SELECT DISTINCT f.foo, b.bar FROM foo_tbl AS f, bar_tbl AS b`, I wind up with every possible combination of rows (first foo first bar, first foo second bar, second foo first bar, second foo second bar, etc etc). Is there a way to do a select like that and having only once instance of each element in a column, and filling the rest of the rows in the column with nulls?

Accepted Answer

You could do something like the following: Assuming table foo has columns a,b,c and table bar has columns d,e,f

```
Select 'isFOO', a, b, c, null, null, null from foo
Union All
Select 'isBAR',null, null, null, d, e, f from bar
```

Joining multiple unrelated tables in MySQL

Solution

Problem