Question

I’m finding it difficult learning how to formulate subqueries in MySQL

For example, this code doesnt seem to be working.

SHOW COLUMNS FROM $table WHERE Field NOT IN (
    SELECT column_name FROM INFORMATION_SCHEMA.COLUMNS
    WHERE table_name = $table
    AND column_name LIKE 'project_images_%'
);

Does anyone have any suggestions? or good resources on subqueries?

Answer 1

Your query is fine, you just forgot the quotes.

SHOW COLUMNS FROM $table WHERE Field NOT IN (
    SELECT column_name FROM INFORMATION_SCHEMA.COLUMNS
    WHERE table_name = '$table' 
    AND column_name LIKE 'project_images_%'
);

Note the quotes added to the where clause in the sub-query.