CODEWITHSUNDEEP
mysql
Baspa
Baspa

Reputation: 1168

Only show the values that does not exist in the other table

I have 2 tables, one with functions and one with used functions. I have a query which only has to show me the values which are not used. So it has to compare if the function name exists in the other table, if not show that value.

For example this is my database table functions:

function_id | function_name | function_description
1           | function_1    | lorem ipsum
2           | function_2    | dolor sit amet

And this is my table used functions:

register_id | function_activation | function_deactivation | etc
1           | function_1          | function_1            | lorem ipsum

So like function_2 does not exist in the used functions table. I used this query to check it:

SELECT * FROM functions WHERE NOT EXISTS 
 (SELECT function_activation, function_deactivation FROM used_functions)

But it shows me nothing. Am I using a wrong query or maybe something else?

Upvotes: 0

Views: 37

Answers (2)

Arnold Daniels
Arnold Daniels

Reputation: 16573

You can do a LEFT JOIN instead of a subquery.

SELECT functions.* FROM functions LEFT JOIN used_functions
  ON functions.function_name = used_functions.function_activation
  WHERE used_functions.function_activation IS NULL

Upvotes: 1

dsharew
dsharew

Reputation: 10665

try like this: 

SELECT * FROM functions WHERE function_name NOT IN
 (SELECT function_activation FROM used_functions)

Upvotes: 2

Related Questions