TASK DEFINITION: In this task you are expected to provide an SQL statement from an english description of what that SQL statement does. The description may include multiple steps but you should only ouput one SQL statement that accomplishes every step. 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: Step 1: For each row in user_profiles table, find the corresponding rows in tweets table.
Step 2: find the number of rows of each value of tweets's uid in the results of step 1.
Step 3: find name, partitionid in the results of step 1 whose corresponding value in step 2 is greater than 2

SOLUTION: SELECT T2.name , T2.partitionid FROM tweets AS T1 JOIN user_profiles AS T2 ON T1.uid = T2.uid GROUP BY T1.uid HAVING Count ( * ) > 2

PROBLEM: find course_id of takes table whose year equals 2010 and semester equals Spring

SOLUTION: SELECT course_id FROM takes WHERE year = 2010 AND semester = "Spring"

PROBLEM: Step 1: find the District_name of district table for which Headquartered_City equals City Mall.
Step 2: For each row in store_district table, find corresponding rows in store table and in district table.
Step 3: find District_name of the results of step 2 whose Type equals Village Store.
Step 4: show the rows that are in both the results of step 1 and the results of step 3

SOLUTION:
SELECT T1.District_name FROM district AS T1 WHERE T1.Headquartered_City = "City Mall" INTERSECT SELECT T1.District_name FROM store AS T2 JOIN district AS T1 JOIN store_district AS T3 ON T2.Store_ID = T3.Store_ID AND T3.District_ID = T1.District_ID WHERE T2.Type = "Village Store"