Using SELECT result as a column name in WHERE clause

Question

What would be the fastest way to delete all records in every table of the database with id = 0 ?

It would be simple if every table had its first column called id , but in my case one table has first column named id_tag , other table - id_product , etc.

I've figured out that I can get the name of the first column by:

SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS 
                        WHERE TABLE_SCHEMA = 'dbname' AND TABLE_NAME = 'ps_tag' LIMIT 1

but how can I include it in a DELETE query? I need something like:

DELETE FROM 'ps_tag' WHERE [first_column] = 0

My first idea was:

DELETE FROM 'ps_tag' 
             WHERE (SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS 
WHERE TABLE_SCHEMA = 'dbname' AND TABLE_NAME = 'ps_tag' LIMIT 1) = 0

but obviously it doesn't work.

Answer 1

This is too long for a comment.

Although you can set up a dynamic SQL statement, I often find this type of operation is easier to do in Excel. Write a query to get the column name and table name for the ones you are interested in.

Then, load these into Excel.

In another cell, put in a string like 'delete from @table where @column = 1' .

Then put in the formula:

=substitute(substitute(<where the string is>, '@table', <tablename>), '@column', <columnname>))

Copy the code back to your database interface and execute it.

(And any spreadsheet will do. I usually have Excel handy.)