Question

I can’t find a mistake in my query:

SELECT
u.Table_Name, 
count(distinct c.Column_Name), 
sum(u.num_rows)    
FROM User_Tab_Columns c, User_Tables u    
WHERE   u.TABLE_NAME = c.TABLE_NAME    
group by u.Table_Name;

the result is:

TABLE_NAME                     COUNT(DISTINCTC.COLUMN_NAME) SUM(U.NUM_ROWS)    
------------------------------ ---------------------------- ---------------
DEPT                                                      3              12     
EMP                                                       8             112

and it should be:

 TABLE_NAME                     COUNT(DISTINCTC.COLUMN_NAME) SUM(U.NUM_ROWS)    
    ------------------------------ ---------------------------- ---------------
    DEPT                                                      3              4     
    EMP                                                       8             14

So the query multiple number of rows and number of columns but I don’t know why?

Answer 1

Since the number of rows is per table, you can simply group by it:

SELECT
u.Table_Name, 
count(*), 
u.num_rows    
FROM User_Tab_Columns c, User_Tables u    
WHERE   u.TABLE_NAME = c.TABLE_NAME    
group by u.Table_Name, u.num_rows;