How to get example values from every column in a schema - mysql

Question

I'm reverse-engineering a MySQL database and I'd like to get a list of example values from every column in every table. I'd like to run a query like this:
select
table_name,
column_name,
group_concat(
(select distinct table_name.column_name limit 100)
separator ','
) as examples
from
information_schema.columns
where
table_schema = 'myschema'
;
I'd like the output to look something like this:
table1 column1 (123,124,234)
table1 column2 ('Joe','Sara','Bob')
MySQL won't accept table_name.column_name as valid syntax. What's the right way to write this query?

Answer 1

I think Sam, you are looking for something like that, or at least it would be a better approach:
select
table_name,
column_name,
group_concat((column_name) separator ',') as examples
from
information_schema.columns
where
table_schema = 'test'
GROUP BY table_name
;

Answer 2

Based on rene's suggestion, I wrote a stored procedure which outputs examples of values from each column in every table. It's ugly and slow, but it works. I'd welcome suggestions on how to improve this code.
DELIMITER //
CREATE PROCEDURE column_example_values(
IN db_name VARCHAR(64),
IN tbl VARCHAR(64),
IN col VARCHAR(64),
OUT result MEDIUMTEXT)
BEGIN
SET #s = CONCAT('SELECT GROUP_CONCAT(tbl1.',col,
' separator \',\') FROM (SELECT DISTINCT ',
col,' FROM ',db_name,'.',tbl,
' LIMIT 100) tbl1 INTO #result1');
PREPARE stmt FROM #s;
EXECUTE stmt;
SET result = IFNULL(#result1,'');
END;
//
DELIMITER ;
DELIMITER //
CREATE PROCEDURE all_columns_example_values(IN db_name VARCHAR(64))
BEGIN
DECLARE done INT DEFAULT FALSE;
DECLARE tbl, col VARCHAR(64);
DECLARE cur1 CURSOR FOR
SELECT
table_name,
column_name
FROM
information_schema.columns
WHERE
table_schema = db_name
ORDER BY
table_name,
column_name;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
CREATE TEMPORARY TABLE results (
tbl VARCHAR(64), col VARCHAR(64), examples MEDIUMTEXT);
OPEN cur1;
read_loop: LOOP
FETCH cur1 INTO tbl, col;
IF done THEN
LEAVE read_loop;
END IF;
CALL column_example_values(db_name,tbl,col,#result);
INSERT INTO results (tbl, col, examples) VALUES (tbl, col, #result);
END LOOP;
CLOSE cur1;
SELECT * FROM results;
DROP TABLE results;
END;
//
DELIMITER ;
It can be called with
CALL all_columns_example_values('mydb');