SQL Exercise: Players who came onto the field during the first half

SQL soccer Database: Joins Exercise-35 with Solution

35. From the following tables, write a SQL query to find the substitute players who entered the field during the first half of play within the normal time frame for the game. Return match_no, country_name, player_name, jersey_no and time_in_out.

Sample table: player_in_out

Sample table: player_mast

Sample table: soccer_country

Sample Solution:

SQL Code:

SELECT match_no,country_name,player_name,jersey_no,time_in_out
FROM player_in_out a
JOIN player_mast b ON a.player_id=b.player_id
JOIN soccer_country c ON b.team_id=c.country_id
WHERE a.in_out='I'
AND a.play_schedule='NT'
AND a.play_half=1
ORDER BY match_no;

Sample Output:

 match_no | country_name |       player_name       | jersey_no | time_in_out
----------+--------------+-------------------------+-----------+-------------
        9 | Sweden       | Erik Johansson          |         3 |          45
       47 | Germany      | Bastian Schweinsteiger  |         7 |          16
       51 | Portugal     | Ricardo Quaresma        |        20 |          25
(3 rows)

Code Explanation:

The given query in SQL that retrieves information about players who were substituted in during the first half of soccer matches that had no extra time, including their name, jersey number, time of substitution, and the country they belong to from the tables player_in_out, player_mast, and soccer_country.
The 'player_in_out' table alias as 'a' joined with the 'player_mast' table alias as 'b' based on the common column "player_id" in 'a' and 'b'. Then, the resulting table is joined with the 'soccer_country' table alias as 'c' based on the common column "team_id" in 'b' and "country_id" in 'c'.
The WHERE clause includes data in the result only rows where the "in_out" column in 'player_in_out' has the value of 'I', the "play_schedule" column has the value of 'NT', and the "play_half" column has the value of 1.
The result set then sorted in ascending order of the "match_no" column.

Relational Algebra Expression:

Relational Algebra Tree:

Practice Online

Sample Database: soccer

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