select column from multiple unknown tables - mysql

Question

I have a lot of dynamically created nearly similar looking tables according to the scheme "prefix + number", eg "t1", "t2", "t343" etc. All those tables have a cross-table unique row named identifier that I like to select within one query:
SELECT
`identifier`
FROM
(
SELECT
`TABLE_NAME`
FROM
information_schema.TABLES
WHERE
`TABLE_NAME` LIKE 't%'
);
But this returns: ERROR 1248 (42000): Every derived table must have its own alias
EDIT: according to the comments I modified my query like this:
SELECT
A.identifier
FROM
(
SELECT
`TABLE_NAME` AS identifier
FROM
information_schema.TABLES
WHERE
`TABLE_NAME` LIKE 't%'
) A;
But this selects only the table names from the subquery but not the column identifier from these tables.

Answer 1

When you create the table dynamically, and you want to query all of them, you can create an SQL statement dynamically like:
select
group_concat(
concat(
'SELECT ',
'''',TABLE_SCHEMA,'.',TABLE_NAME,''',',
TABLE_SCHEMA,'.',TABLE_NAME,'.', COLUMN_NAME,
' FROM ',
TABLE_SCHEMA,'.',TABLE_NAME)
separator ' union all ')
from information_schema.`COLUMNS` c
where table_schema='test' -- the schema name where your tables are
and table_name regexp '^t[0-9]+$' -- table name starts with t and ends with number
and COLUMN_NAME = 'i' -- i choose `i` as the column to be selected
;
This will produce a SQL statement like:
select
'test.t1',
test.t1.i
from
test.t1
union all
select
'test.t2',
test.t2.i
from
test.t2
union all
select
'test.t3',
test.t3.i
from
test.t3
When putting all of this in a stored procedure, you can use PREPARE and EXECUTE to execute this created statement.
Above is just an example of an SQL statement, you should change it to your needs.