TASK DEFINITION: In this task you are expected to fix an SQL query based on feedback. You will be given an SQL statement and an English description with what is wrong about that SQL statement. You must correct the SQL statement based off of the feedback. An SQL query works by selecting data from a table where certain conditions apply. A table contains columns where every row in that table must have a value for each column. Every table has a primary key that uniquely identifies each row, usually an id. To choose which columns are returned you specify that after the "SELECT" statement. Next, you use a "FROM" statement to specify what tables you want to select the data from. When you specify a table you can rename it with the "AS" statement. You can reference that table by whatever name follows the "AS" statement. If you want to select data from multiple tables you need to use the "JOIN" statement. This will join the tables together by pairing a row in one table with every row in the other table (Cartesian Product). To limit the number of rows returned you should use the "ON" statement. This will only return rows where the condition specified after the statement is true, this is usually an equals operator with primary keys. You can also use the "WHERE" statement to specify that only rows with column values statisfying a certain condition, should be returned. The "GROUP BY" statement will group rows together that have equal column values for whatever columns follows the statement. The "HAVING" statement will return groups that statisfy whatever condition follows the statement. Any column(s) being returned from grouped rows must either be an aggregate function, (AVG, MAX, COUNT, SUM, ...) of a column, or the column(s) that the data was grouped by. To sort the returned data you can use the "ORDER BY" command which will order the data by whatever aggregate function or column follows the statement. The "DESC" statement will sort in descending order and the "ASC" statement will sort in ascending order. Finally, you can use the "LIMIT" statement to return a certain number of rows. When "*" is used in an SQL statement every column is returned. For example, SELECT * FROM table WHERE attribute = 1, will select every column from rows with the attribute column equal to 1. 
PROBLEM: SQL: SELECT supplier_id FROM Product_Suppliers GROUP BY product_id HAVING Avg ( total_value_purchased ) > 50000
Feedback: Replace total value purchased with total amount purchased , corresponding step 1 value should be greater than 50000 or less than 30000.

SOLUTION: SELECT supplier_id FROM Product_Suppliers GROUP BY supplier_id HAVING avg(total_amount_purchased)  >  50000 OR avg(total_amount_purchased)  <  30000

PROBLEM: SQL: SELECT winner_name , loser_rank FROM matches ORDER BY winner_rank_points Desc LIMIT 1
Feedback: Find winner name whose tourney name equals Australian Open with largest value of winner rank points .

SOLUTION: SELECT winner_name FROM matches WHERE tourney_name  =  'Australian Open' ORDER BY winner_rank_points DESC LIMIT 1

PROBLEM: SQL: SELECT T1.name , Avg ( T2.duration ) FROM station AS T1 JOIN trip AS T2 GROUP BY T2.start_station_id
Feedback: need to final longitude of station as well

SOLUTION:
SELECT T1.name ,  T1.long ,  avg(T2.duration) FROM station AS T1 JOIN trip AS T2 ON T1.id  =  T2.start_station_id GROUP BY T2.start_station_id