Question

在sql表中

我在第一栏有100个公司名称。在接下来的20个栏目中有20个月，比如2011年7月，...... 2012年7月......（这些月份列包含每个公司的数字需求数据）

我想只有3列：公司名称，月份，需求。（每个公司名称将重复20次）

如何使用sql代码转换它？

Answer 1

我的建议是规范化您的数据库。您应该创建至少2个表：

company: 
- id
- name

value:
- company_id
- value
- month (numeric)

然后您可以将每个值（在“值”表中）与相应的公司和相应的月份相关联。

Answer 2

使用unpivot命令。此示例占用一行并将其转换为两行。

以下示例需要两行并将其转换为四行。

    WITH xset
         AS (SELECT 'Expedition' ford
                  , 'Corvette' gm
                  , DATE '2013-01-01' ford_raise
                  , DATE '2013-09-03' gm_raise
                  , 1 seq
               FROM DUAL
             UNION ALL
             SELECT 'Fusion'
                  , 'Escalate'
                  , DATE '2010-07-04'
                  , DATE '2001-12-31'
                  , 2
               FROM DUAL)
    SELECT *
      FROM xset UNPIVOT ((event_date, model) FOR event IN ((ford_raise, ford) AS 'Ford Raise', (gm_raise, gm) AS 'GM Raise'))

Answer 3

据我所知，MySQL中没有UNPIVOT函数，因此您需要使用UNION ALL执行此操作：

SQL Fiddle

MySQL 5.5.32架构设置：

CREATE TABLE MyTable
    (`id` int, `name` varchar(5), `m1` int, `m2` int, `m3` int, `m4` int, `m5` int, `m6` int, `m7` int, `m8` int, `m9` int, `m10` int, `m11` int, `m12` int, `m13` int, `m14` int, `m15` int, `m16` int, `m17` int, `m18` int, `m19` int, `m20` int)
;

INSERT INTO MyTable
    (`id`, `name`, `m1`, `m2`, `m3`, `m4`, `m5`, `m6`, `m7`, `m8`, `m9`, `m10`, `m11`, `m12`, `m13`, `m14`, `m15`, `m16`, `m17`, `m18`, `m19`, `m20`)
VALUES
    (1, 'name1', 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20),
    (2, 'name2', 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20),
    (3, 'name3', 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
;

CREATE TABLE Company
    ( id INT NOT NULL AUTO_INCREMENT, name CHAR(30), PRIMARY KEY (id))
;

CREATE TABLE Demand
    (`id` INT NOT NULL AUTO_INCREMENT, `company_id` int,  `month` varchar(3), `value` varchar(5), PRIMARY KEY (id))
;

INSERT INTO Company 
SELECT id,name FROM Mytable;

INSERT INTO Demand (company_id, month, value) 
SELECT id,'m1' as month, m1 as value FROM Mytable
UNION ALL
SELECT id,'m2' as month, m2 as value FROM Mytable
UNION ALL
SELECT id,'m3' as month, m3 as value FROM Mytable
UNION ALL
SELECT id,'m4' as month, m4 as value FROM Mytable
UNION ALL
SELECT id,'m5' as month, m5 as value FROM Mytable
UNION ALL
SELECT id,'m6' as month, m6 as value FROM Mytable
UNION ALL
SELECT id,'m7' as month, m7 as value FROM Mytable
UNION ALL
SELECT id,'m8' as month, m8 as value FROM Mytable
UNION ALL
SELECT id,'m9' as month, m9 as value FROM Mytable
UNION ALL
SELECT id,'m10' as month, m10 as value FROM Mytable
UNION ALL
SELECT id,'m11' as month, m11 as value FROM Mytable
UNION ALL
SELECT id,'m12' as month, m12 as value FROM Mytable
UNION ALL
SELECT id,'m13' as month, m13 as value FROM Mytable
UNION ALL
SELECT id,'m14' as month, m14 as value FROM Mytable
UNION ALL
SELECT id,'m15' as month, m15 as value FROM Mytable
UNION ALL
SELECT id,'m16' as month, m16 as value FROM Mytable
UNION ALL
SELECT id,'m17' as month, m17 as value FROM Mytable
UNION ALL
SELECT id,'m18' as month, m18 as value FROM Mytable
UNION ALL
SELECT id,'m19' as month, m19 as value FROM Mytable
UNION ALL
SELECT id,'m20' as month, m20 as value FROM Mytable

SQL从多列转换为几列？

3 个答案: