查找外键引用字段的值

Question

I have here an SQL query that I got from this source . What it does is it finds all the primary keys and their references in the database.

select
    concat(table_name, '.', column_name) as 'foreign key',  
    concat(referenced_table_name, '.', referenced_column_name) as 'references'
from
    information_schema.key_column_usage
where
    referenced_table_name is not null
    and table_schema = 'my_database'

I modified it a little to become this

select
    table_name as fk_table_name, column_name as 'foreign key',  
    referenced_table_name as ref_table_name, referenced_column_name as 'references'
from
    information_schema.key_column_usage
inner join
    information_schema.referenced_table_name
where
    referenced_table_name is not null
    and column_name = 'customer_number'
    and referenced_table_name = 'accepted_orders'

Now it doesn't work. The error it returns is ' #1109 - Unknown table 'referenced_table_name' in information_schema'. My goal is instead of just displaying what the referenced column name is, it gives me all the values of that column instead.

So instead of telling me that the foreign key customer_number in accepted_orders references the primary key customer_number in customer_records, I want to get all the values of customer_number in customer_records instead.

I thought of using an inner join on the result of the query but apparently it won't let me. How do I do this? Do I have to use separate SQL statements?

Answer 1

You seem to be, as the error message says, using referenced_table_name in a context where the query parser wants a table name, not a column name. You wrote:

inner join
   information_schema.referenced_table_name

That doesn't make any sense because you're trying to join to a column, not a table.

Try omitting the two lines above from your query.