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 players table, find the corresponding rows in matches table.
Step 2: find first_name, country_code of the results of step 1 whose loser_ioc equals WTA Championships.
Step 3: find first_name, country_code of the results of step 1 whose loser_ioc equals Australian Open.
Step 4: show the rows that are in both the results of step 2 and the results of step 3

SOLUTION: SELECT T1.first_name , T1.country_code FROM players AS T1 JOIN matches AS T2 ON T1.player_id = T2.loser_id WHERE T2.loser_ioc = "WTA Championships" INTERSECT SELECT T1.first_name , T1.country_code FROM players AS T1 JOIN matches AS T2 ON T1.player_id = T2.loser_id WHERE T2.loser_ioc = "Australian Open"

PROBLEM: find country of circuits table whose lat greater than 2017 and circuitRef equals Spain

SOLUTION: SELECT country FROM circuits WHERE lat > 2017 AND circuitRef = "Spain"

PROBLEM: find the name of aircraft table for which name contains 99

SOLUTION:
SELECT name FROM aircraft WHERE name LIKE 99