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 staff_name , staff_gender FROM Staff WHERE staff_name = "2016%"
Feedback: Replace staff name with date assigned from of staff department assignments table .

SOLUTION: SELECT T1.staff_name ,  T1.staff_gender FROM staff AS T1 JOIN staff_department_assignments AS T2 ON T1.staff_id  =  T2.staff_id WHERE T2.date_assigned_from LIKE "2016%"

PROBLEM: SQL: SELECT Continent FROM country GROUP BY Continent ORDER BY Count ( * ) Desc LIMIT 1
Feedback: Need to find country's name where maximum languages are used in that country .

SOLUTION: SELECT T1.Name FROM country AS T1 JOIN countrylanguage AS T2 ON T1.Code  =  T2.CountryCode GROUP BY T1.Name ORDER BY COUNT(*) DESC LIMIT 1

PROBLEM: SQL: SELECT Type FROM Institution WHERE Enrollment > 1000 INTERSECT SELECT Type FROM Institution WHERE Enrollment < 1990
Feedback: enrollment greater than or equals 1000 step1 , founded greater than 1990 instead enrollment less than 1990 step 2.

SOLUTION:
SELECT TYPE FROM institution WHERE founded  >  1990 AND enrollment  >=  1000