Join all tables with same structure in one MYSQL - mysql

Question

I'm working on an old database already in use for years and really crappy designed.
There is a table, "Articles", which contains a "code" column that will be our PK.
And many tables like "idXXXXX" where XXXXX is a "code" value with exactly the same structure.
I looked at the application using this database and saw that relations between tables is made there.
I'm not affraid of redesign the database access in the application, but I don't want to lose years of entries in the database.
I want to create a "campain" table which will have an "id" PK and a "id_code" as FK linking "campain" to "articles"
I'm not a SQL master but I know I can get tables names with
SELECT TABLE_NAME FROM INFORMATION_SCHEMA WHERE TABLE_NAME LIKE 'id%'
But I have really no idea about how to deal with the result (which is fine).
So how can I access to every tables named "idXXX" and insert every rows in the "campain" table + set "id_code" column to "XXX"?
Here is the procedure I saved (I didn't add every fields in the INSERT line for testing purpose) :
CREATE PROCEDURE JoinAllTables()
BEGIN
DECLARE done INT default 0;
DECLARE tableName CHAR(9);
DECLARE buffStr CHAR(7);
DECLARE buffId INT default 0;
DECLARE cur1 CURSOR FOR SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME LIKE 'id%';
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cur1;
read_loop: LOOP
FETCH cur1 INTO tableName;
IF done THEN
LEAVE read_loop;
END IF;
SET buffStr = SUBSTRING(tableName, 3);
SET buffId = CAST(buffStr AS SIGNED);
set #sql = CONCAT("INSERT INTO campagnes(id, id_code) SELECT null, bufId FROM ",tableName); # Dynamically building sql statement
PREPARE stmt FROM #sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END LOOP;
CLOSE cur1;
END;
As u can see, I sub 'idXXXXX' to 'XXXXX' then CAST it AS INTEGER (SIGNED).
But I guess that in the "INSERT INTO" line, second tableName doesn't point to the variable. That's why I'm getting a
"#1446 - Tabble 'bddsoufflage.tablename'doesn't exist" Error :) Any idea ?

Answer 1

Edit: Updated answer
We can't have the tableName dynamically changed inside a prepared statement, so we must go through DynamicSQL to build the query using CONCAT, then compile the SQL with PREPARE, EXECUTE it and DEALLOCATE it.
DELIMITER //
CREATE PROCEDURE JoinAllTables()
BEGIN
DECLARE done INT default 0;
DECLARE tableName CHAR(9);
DECLARE buffStr CHAR(7);
DECLARE buffId INT default 0;
DECLARE cur1 CURSOR FOR SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME LIKE 'id%';
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cur1;
read_loop: LOOP
FETCH cur1 INTO tableName;
IF done THEN
LEAVE read_loop;
END IF;
SET buffStr = SUBSTRING(tableName, 3);
SET buffId = CAST(buffStr AS SIGNED);
set #sql = CONCAT("INSERT INTO campagnes(id, id_code) SELECT null, ", buffId, " FROM ",tableName); # Dynamically building sql statement
PREPARE stmt FROM #sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END LOOP;
CLOSE cur1;
END; //
See also this answer MySQL Pass table name to cursor select
Old answer
The procedure should look something like this. Thanks Mchl for providing an Insert Into query example, I simply added it to the rest of the procedure.
DELIMITER //
CREATE PROCEDURE JoinAllTables()
BEGIN
DECLARE done INT default 0;
DECLARE tableName CHAR(7); # Variable to contain table names CHAr(7) is assuming id + 5Xs as characters.
DECLARE cur1 CURSOR FOR SELECT TABLE_NAME FROM INFORMATION_SCHEMA WHERE TABLE_NAME LIKE 'id%'; # Create a cursor to iterate over the tables
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cur1;
read_loop: LOOP
FETCH cur1 INTO tableName;
IF done THEN
LEAVE read_loop;
END IF;
#Your Insert statement here, using tableName as a field.
INSERT INTO campain (id, id_code, otherfields) SELECT null, tableName, otherfields FROM tableName;
END LOOP;
CLOSE cur1;
END;//

Answer 2

Easiest way would be to run the information_schema query you have within some script (PHP,Python,Perl - whichever suits you best) and use it's results to create queries like:
INSERT INTO
campain (id, id_code, otherfields)
SELECT
null, 'idXXXX', otherfields FROM idXXXX