Use CASE WHEN statement in SELECT 2 : CASE WHEN Select « Flow Control « SQL / MySQL

1. SQL / MySQL
2. Flow Control
3. CASE WHEN Select

Use CASE WHEN statement in SELECT 2

/*
mysql> SELECT Name, RatingID AS Rating,
    ->    CASE
    ->       WHEN RatingID='R' THEN 'Under 17 requires an adult.'
    ->       WHEN RatingID='X' THEN 'No one 17 and under.'
    ->       WHEN RatingID='NR' THEN 'Use discretion when renting.'
    ->       ELSE 'OK to rent to minors.'
    ->    END AS Policy
    -> FROM DVDs
    -> ORDER BY Name;
+-----------+--------+------------------------------+
| Name      | Rating | Policy                       |
+-----------+--------+------------------------------+
| Africa    | PG     | OK to rent to minors.        |
| Amadeus   | PG     | OK to rent to minors.        |
| Christmas | NR     | Use discretion when renting. |
| Doc       | G      | OK to rent to minors.        |
| Falcon    | NR     | Use discretion when renting. |
| Mash      | R      | Under 17 requires an adult.  |
| Show      | NR     | Use discretion when renting. |
| View      | NR     | Use discretion when renting. |
+-----------+--------+------------------------------+
8 rows in set (0.01 sec)


*/

Drop table DVDs;

CREATE TABLE DVDs (
   ID SMALLINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
   Name VARCHAR(60) NOT NULL,
   NumDisks TINYINT NOT NULL DEFAULT 1,
   RatingID VARCHAR(4) NOT NULL,
   StatID CHAR(3) NOT NULL
)
ENGINE=INNODB;

INSERT INTO DVDs (Name, NumDisks, RatingID, StatID)
VALUES ('Christmas', 1, 'NR', 's1'),
       ('Doc',       1, 'G',  's2'),
       ('Africa',    1, 'PG', 's1'),
       ('Falcon',    1, 'NR', 's2'),
       ('Amadeus',   1, 'PG', 's2'),
       ('Show',      2, 'NR', 's2'),
       ('View',      1, 'NR', 's1'),
       ('Mash',      2, 'R',  's2');
  

SELECT Name, RatingID AS Rating,
   CASE
      WHEN RatingID='R' THEN 'Under 17 requires an adult.'
      WHEN RatingID='X' THEN 'No one 17 and under.'
      WHEN RatingID='NR' THEN 'Use discretion when renting.'
      ELSE 'OK to rent to minors.'
   END AS Policy
FROM DVDs
ORDER BY Name;


           
       

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