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mysqlsqlinner-join

DESC joined tables

Is there a way to describe the columns of a joined table in SQL?

If I have just one table, for example A I can do

DESC A

But how can I show the columns of a joined table? Something like

DESC A INNER JOIN B on A.id_a = B.id_b
Solution

  • DESCRIBE is a synonym for SHOW COLUMNS. That only works for tables and views.

    To get that to work for a "join" of two tables, if we have sufficient privileges, we could create view object, e.g

    CREATE VIEW _temp_ AS SELECT a.*, b.* FROM a JOIN b ON a.id_a = b.id_b

    and then we could do a SHOW COLUMNS from the view: 

    SHOW COLUMNS FROM _temp_ ;

    We can get the same result using one of the aliases for SHOW COLUMNS ... 

    DESCRIBE _temp_ ;

    or 

    EXPLAIN _temp_ ;

    Then we should drop the view:

    DROP VIEW _temp_ ;

    (It's not entirely clear what problem we are attempting to solve; I only addressed the question that was asked, how to get DESC to work for an inner join.)