SQL/MySQL/Flow Control/IF — различия между версиями

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Текущая версия на 10:16, 26 мая 2010

Use IF in select clause

/*
mysql> select * from sales;
+-----+------------+--------+--------+--------+------+------------+
| num | name       | winter | spring | summer | fall | category   |
+-----+------------+--------+--------+--------+------+------------+
|   1 | Java       |   1067 |    200 |    150 |  267 | Holiday    |
|   2 | C          |    970 |    770 |    531 |  486 | Profession |
|   3 | JavaScript |     53 |     13 |     21 |  856 | Literary   |
|   4 | SQL        |    782 |    357 |    168 |  250 | Profession |
|   5 | Oracle     |    589 |    795 |    367 |  284 | Holiday    |
|   6 | MySQL      |    953 |    582 |    336 |  489 | Literary   |
|   7 | Cplus      |    752 |    657 |    259 |  478 | Literary   |
|   8 | Python     |     67 |     23 |     83 |  543 | Holiday    |
|   9 | PHP        |    673 |     48 |    625 |   52 | Profession |
+-----+------------+--------+--------+--------+------+------------+
9 rows in set (0.01 sec)
mysql> SELECT name AS Name, category AS Category,
    -> IF(winter>500, "Sells", "Slow") AS Trend
    -> FROM sales;
+------------+------------+-------+
| Name       | Category   | Trend |
+------------+------------+-------+
| Java       | Holiday    | Sells |
| C          | Profession | Sells |
| JavaScript | Literary   | Slow  |
| SQL        | Profession | Sells |
| Oracle     | Holiday    | Sells |
| MySQL      | Literary   | Sells |
| Cplus      | Literary   | Sells |
| Python     | Holiday    | Slow  |
| PHP        | Profession | Sells |
+------------+------------+-------+
9 rows in set (0.00 sec)

*/
Drop table sales;
  
CREATE TABLE sales(
    num MEDIUMINT NOT NULL AUTO_INCREMENT,
    name CHAR(20),
    winter INT,
    spring INT,
    summer INT,
    fall INT,
    category CHAR(13),
    primary key(num)
)type=MyISAM;

insert into sales value(1, "Java", 1067 , 200, 150, 267,"Holiday");
insert into sales value(2, "C",970,770,531,486,"Profession");
insert into sales value(3, "JavaScript",53,13,21,856,"Literary");
insert into sales value(4, "SQL",782,357,168,250,"Profession");
insert into sales value(5, "Oracle",589,795,367,284,"Holiday");
insert into sales value(6, "MySQL",953,582,336,489,"Literary");
insert into sales value(7, "Cplus",752,657,259,478,"Literary");
insert into sales value(8, "Python",67,23,83,543,"Holiday");
insert into sales value(9, "PHP",673,48,625,52,"Profession");
select * from sales;
  
SELECT name AS Name, category AS Category,
IF(winter>500, "Sells", "Slow") AS Trend
FROM sales;