MYSQL - SELECT data from dynamic table names

Question

Imagine that I have several dynamic table names such as :

select table_name
from INFORMATION_SCHEMA.TABLES
where table_name like 'ifhcraw%';
ifhcraw_2016_03_25_13
ifhcraw_2016_03_26_19
ifhcraw_2016_03_28_2

And I don't found any rule on names. To find last edited table I have just select last modified table with query :

select table_name
from INFORMATION_SCHEMA.TABLES
where table_name like 'ifhcraw%' and
      update_time = (select max(update_time)
                     from INFORMATION_SCHEMA.TABLES
                     where table_name like 'ifhcraw%');

Now the purpose all of this step to get data from table_name. I have tried to use variables , however it was failed. For example :

SET @query1 := 'select table_name
                from INFORMATION_SCHEMA.TABLES
                where table_name like \'ifhcraw%\' and
                update_time = (select max(update_time)
                               from INFORMATION_SCHEMA.TABLES
                               where table_name like \'ifhcraw%\') ';
SET @query2 := concat('select *
                       from ', @query1);
PREPARE stmt from @query2;
execute stmt;

Please help to solve issue.

Can you use merge or partitioned tables instead of tables with similar names? If not, then what was the exact error message you encountered while running the prepared statement? — Shadow
– Shadow, Commented Apr 1, 2016 at 10:47
I have got message: SQL (1064): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'select table_name from INFORMATION_SCHEMA.TABLES where table_name like 'ifhcraw%' at line 1 */ — Javid
– Javid, Commented Apr 1, 2016 at 11:38
SET @query2 := concat('select * from ', /*@query1:*/'select table_name ...');. Try PREPARE stmt from @query1;. — wchiquito
– wchiquito, Commented Apr 1, 2016 at 12:33

wchiquito · Accepted Answer · 2016-04-07 09:43:56Z

Try:

mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.7.11    |
+-----------+
1 row in set (0.00 sec)

mysql> DROP TABLE IF EXISTS `ifhcraw_2016_03_25_13`;
Query OK, 0 rows affected (0.00 sec)

mysql> DROP TABLE IF EXISTS `ifhcraw_2016_03_26_19`;
Query OK, 0 rows affected (0.00 sec)

mysql> DROP TABLE IF EXISTS `ifhcraw_2016_03_28_2`;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE `ifhcraw_2016_03_25_13` (
    ->   `id` INT
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE `ifhcraw_2016_03_26_19` (
    ->   `id` INT
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE `ifhcraw_2016_03_28_2` (
    ->   `id` INT
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql> SET @`TABLE_NAME` := NULL;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT `TABLE_NAME` INTO @`TABLE_NAME`
    -> FROM `INFORMATION_SCHEMA`.`TABLES`
    -> WHERE `TABLE_NAME` LIKE 'ifhcraw%' AND
    ->       `UPDATE_TIME` = (SELECT MAX(`UPDATE_TIME`)
    ->                        FROM `INFORMATION_SCHEMA`.`TABLES`
    ->                        WHERE `TABLE_NAME` LIKE 'ifhcraw%'
    ->                       );
Query OK, 0 rows affected, 1 warning (0.01 sec)

mysql> SELECT @`TABLE_NAME`;
+---------------+
| @`TABLE_NAME` |
+---------------+
| NULL          |
+---------------+
1 row in set (0.00 sec)

mysql> SET @`qry` := IF(@`TABLE_NAME` IS NULL,
    ->                  'SELECT NULL',
    ->                  CONCAT('SELECT * FROM ', @`TABLE_NAME`));
Query OK, 0 rows affected (0.00 sec)

mysql> PREPARE `stmt` FROM @`qry`;
Query OK, 0 rows affected (0.00 sec)
Statement prepared

mysql> EXECUTE `stmt`;
+------+
| NULL |
+------+
| NULL |
+------+
1 row in set (0.00 sec)

mysql> DEALLOCATE PREPARE `stmt`;
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO `ifhcraw_2016_03_26_19`
    ->   (`id`)
    -> VALUES
    ->   (1);
Query OK, 1 row affected (0.00 sec)

mysql> SELECT `TABLE_NAME` INTO @`TABLE_NAME`
    -> FROM `INFORMATION_SCHEMA`.`TABLES`
    -> WHERE `TABLE_NAME` LIKE 'ifhcraw%' AND
    ->       `UPDATE_TIME` = (SELECT MAX(`UPDATE_TIME`)
    ->                        FROM `INFORMATION_SCHEMA`.`TABLES`
    ->                        WHERE `TABLE_NAME` LIKE 'ifhcraw%'
    ->                       );
Query OK, 1 row affected (0.00 sec)

mysql> SELECT @`TABLE_NAME`;
+-----------------------+
| @`TABLE_NAME`         |
+-----------------------+
| ifhcraw_2016_03_26_19 |
+-----------------------+
1 row in set (0.00 sec)

mysql> SET @`qry` := IF(@`TABLE_NAME` IS NULL,
    ->                  'SELECT NULL',
    ->                  CONCAT('SELECT * FROM ', @`TABLE_NAME`));
Query OK, 0 rows affected (0.00 sec)

mysql> PREPARE `stmt` FROM @`qry`;
Query OK, 0 rows affected (0.00 sec)
Statement prepared

mysql> EXECUTE `stmt`;
+------+
| id   |
+------+
|    1 |
+------+
1 row in set (0.00 sec)

mysql> DEALLOCATE PREPARE `stmt`;
Query OK, 0 rows affected (0.00 sec)

UPDATE

Care should be taken when there are two or more tables that match the criteria, will fail as follows:

mysql> INSERT INTO `ifhcraw_2016_03_26_19`
    ->   (`id`)
    -> VALUES
    ->   (1);
Query OK, 1 row affected (0,00 sec)

mysql> INSERT INTO `ifhcraw_2016_03_28_2`
    ->   (`id`)
    -> VALUES
    ->   (1);
Query OK, 1 row affected (0,00 sec)

mysql> SELECT `TABLE_NAME`
    -> FROM `INFORMATION_SCHEMA`.`TABLES`
    -> WHERE `TABLE_NAME` LIKE 'ifhcraw%' AND
    ->       `UPDATE_TIME` = (SELECT MAX(`UPDATE_TIME`)
    ->                        FROM `INFORMATION_SCHEMA`.`TABLES`
    ->                        WHERE `TABLE_NAME` LIKE 'ifhcraw%'
    ->                       );
+-----------------------+
| TABLE_NAME            |
+-----------------------+
| ifhcraw_2016_03_26_19 |
| ifhcraw_2016_03_28_2  |
+-----------------------+
2 rows in set (0,00 sec)

mysql> SELECT `TABLE_NAME` INTO @`TABLE_NAME`
    -> FROM `INFORMATION_SCHEMA`.`TABLES`
    -> WHERE `TABLE_NAME` LIKE 'ifhcraw%' AND
    ->       `UPDATE_TIME` = (SELECT MAX(`UPDATE_TIME`)
    ->                        FROM `INFORMATION_SCHEMA`.`TABLES`
    ->                        WHERE `TABLE_NAME` LIKE 'ifhcraw%'
    ->                       );
ERROR 1172 (42000): Result consisted of more than one row

You should handle the case as you deem appropriate.

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