Stored Procedure to read text file and loop through it - mysql

Question

I tried looking through a lot of threads on this but couldn't find anything that works for me.
I have a text file with list of table names (about 100 out of 300 total tables in the schema).
tables.txt
table1
table2
table3
I am writing a stored procedure and want to loop through the table names in that text file and inject the table names in the query.
Something like this
While (line = readline) != null do
update line set col1='foo' where id=x;
End while;
Is something like that even possible in a stored procedure? using (mysql 5.6). and I am using Workbench 6.3 CE

Answer 1

Since you want to run the same code for every table in your database.You can create your command using Information Schema
USE INFORMATION_SCHEMA;
SELECT
CONCAT("ALTER TABLE `", TABLE_SCHEMA,"`.`", TABLE_NAME, "` ALTERING CODE HERE;")
AS MySQLCMD FROM TABLES
WHERE TABLE_SCHEMA = "your_schema_goes_here";
When the commands are created then you can copy and run all of them.
UPDATE If you want to update a column common between all those tables you can write it as follow
SELECT CONCAT("UPDATE `", TABLE_SCHEMA,"`.`", TABLE_NAME, "` SET COLUMN_NAME = VALUE [ANY WHERE CLAUSE]") as MySQLCMD from TABLES where TABLE_SCHEMA = "YourSchemaName";
UPDATE2 Generating commands for specific tables.
SELECT
CONCAT("ALTER TABLE `", TABLE_SCHEMA,"`.`", TABLE_NAME, "` ALTERING CODE HERE;")
AS MySQLCMD FROM TABLES
WHERE TABLE_SCHEMA = "your_schema_goes_here" AND TABLE_NAME IN ('Table1', 'TAble2');

Answer 2

In general I would take this approach. There is not enough detail to be more specific. Note, this uses dynamic SQL rather than a stored procedure.
Backup your database!!
Create a temporary table. (either real or in memory depending on how long you need this data retained)
Parse the text file into a temporary table using something like this:
LOAD DATA INFILE '/tmp/mylist.txt' INTO TABLE MyTempList;
Create a test a single ALTER table statement. Once you know it works exactly as intended...
Convert your working ALTER statement into dynamic SQL that selects the table names from your temporary table. Something like this: Alter table using sub select
When complete, you can delete your temporary table.
Alternately, you could put a single ALTER statement into a stored procedure, asking for the table name as a parameter. But then you will still need to parse the text file using something like steps 1-3. And then use a cursor to loop over the table names and call the stored procedure.