Question

I’m trying to select all tables from a specified database that contain columns ‘lang’ and ‘project’. This is what i’m doing:

SELECT DISTINCT(ISC1.TABLE_NAME) AS `table` FROM INFORMATION_SCHEMA.COLUMNS AS ISC1 
JOIN INFORMATION_SCHEMA.COLUMNS AS ISC2 ON 
    (ISC1.TABLE_SCHEMA=ISC2.TABLE_SCHEMA AND ISC1.TABLE_NAME=ISC2.TABLE_NAME AND ISC2.COLUMN_NAME='project') 
WHERE ISC1.COLUMN_NAME='lang' AND ISC2.COLUMN_NAME='project' AND ISC1.TABLE_SCHEMA='some_database'

• It does work, but i have a feeling it is a bad way to write this kind of query. If someone can improve on it, that would be nice.
• Now i have to change this query to select all tables that have ‘lang’ column, but do NOT have ‘project’ column. And honestly i can’t figure out where to start…

Thanks for your help

Answer 1

SELECT DISTINCT(ISC1.TABLE_NAME) AS `table`
FROM INFORMATION_SCHEMA.COLUMNS AS ISC1,
    INFORMATION_SCHEMA.COLUMNS AS ISC2 
WHERE ISC1.TABLE_SCHEMA=ISC2.TABLE_SCHEMA
AND ISC1.TABLE_NAME=ISC2.TABLE_NAME
AND ISC2.COLUMN_NAME='project'
AND ISC1.COLUMN_NAME='lang'
AND ISC1.TABLE_SCHEMA='some_database'

Without project column :

SELECT DISTINCT(ISC.TABLE_NAME) AS `table`
FROM INFORMATION_SCHEMA.COLUMNS AS ISC
WHERE ISC.COLUMN_NAME='lang'
AND ISC.TABLE_SCHEMA='some_database'
AND NOT EXISTS(SELECT *
    FROM INFORMATION_SCHEMA.COLUMNS C
    WHERE C.COLUMN_NAME = 'project'
    AND C.TABLE_NAME=ISC.TABLE_NAME
    AND C.TABLE_SCHEMA=ISC.TABLE_SCHEMA)