Question

I have 4 table, default_table, table_a, table_b, table_c, each have two columns,
I want to select name and id from all table then sort it,
I try"SELECT Name,ID FROM default_table, table_a, table_b, table_c ORDER BY Name"
but this give me error, so can someone help me with this problem, i need code in sql or php, or even javascript if it can

Answer 1

Since order by is applied after unioning, you can just do:

select id, name from default_table
    union all select id, name from table_a
    union all select id, name from table_b
    union all select id, name from table_c
order by name

Your problem is that you’re doing a Cartesian product of all the table data so it’s can’t figure out which id or name you mean. Even if it could, you’d get way more rows than you’d expect, due to the multiplicative effect. You want to join the data simply by adding all the rows to the output.

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Explaining the distinction further, let’s say you have two tables:

table1          table2
======          ======
id     name     id     name
--     ----     --     ------
 1     pax       1     jill
 2     bob       2     debbie
 3     joe

The query:

select a.id, a.name, b.id, b.name from table1 a, table2 b

(the cartesian product) will give you:

1 pax 1 jill
1 pax 2 debbie
2 bob 1 jill
2 bob 2 debbie
3 joe 1 jill
3 joe 2 debbie

(the row count is the product of the individual row counts) whereas:

select id, name from table1
union all
select id, name from table2

(the union) will give you:

1 pax
2 bob
3 joe
1 jill
2 debbie

(the row count is the sum of the individual row counts).