利用 SQL 实现行转列和列转行操作
行转列，列转行是我们在开发过程中经常碰到的问题。行转列一般通过CASE WHEN 语句来实现，也可以通过 SQL SERVER 的运算符PIVOT来实现。用传统的方法，比较好理解。层次清晰，而且比较习惯。但是PIVOT 、UNPIVOT提供的语法比一系列复杂的SELECT…CASE 语句中所指定的语法更简单、更具可读性。下面我们通过几个简单的例子来介绍一下列转行、行转列问题。
CREATE TABLE [StudentScores]
(
[UserName] NVARCHAR(20), --学生姓名
[Subject] NVARCHAR(30), --科目
[Score] FLOAT, --成绩
)
INSERT INTO [StudentScores] SELECT 'Nick', '语文', 80
INSERT INTO [StudentScores] SELECT 'Nick', '数学', 90
INSERT INTO [StudentScores] SELECT 'Nick', '英语', 70
INSERT INTO [StudentScores] SELECT 'Nick', '生物', 85
INSERT INTO [StudentScores] SELECT 'Kent', '语文', 80
INSERT INTO [StudentScores] SELECT 'Kent', '数学', 90
INSERT INTO [StudentScores] SELECT 'Kent', '英语', 70
INSERT INTO [StudentScores] SELECT 'Kent', '生物', 85
(提示：可以左右滑动代码)
SELECT
UserName,
MAX(CASE Subject WHEN '语文' THEN Score ELSE 0 END) AS '语文',
MAX(CASE Subject WHEN '数学' THEN Score ELSE 0 END) AS '数学',
MAX(CASE Subject WHEN '英语' THEN Score ELSE 0 END) AS '英语',
MAX(CASE Subject WHEN '生物' THEN Score ELSE 0 END) AS '生物'
FROM dbo.[StudentScores]
GROUP BY UserName
CREATE TABLE [Inpours]
(
[ID] INT IDENTITY(1,1),
[UserName] NVARCHAR(20), --游戏玩家
[CreateTime] DATETIME, --充值时间
[PayType] NVARCHAR(20), --充值类型
[Money] DECIMAL, --充值金额
[IsSuccess] BIT, --是否成功 1表示成功， 0表示失败
CONSTRAINT [PK_Inpours_ID] PRIMARY KEY(ID)
)
INSERT INTO Inpours SELECT '张三', '2010-05-01', '支付宝', 50, 1
INSERT INTO Inpours SELECT '张三', '2010-06-14', '支付宝', 50, 1
INSERT INTO Inpours SELECT '张三', '2010-06-14', '手机短信', 100, 1
INSERT INTO Inpours SELECT '李四', '2010-06-14', '手机短信', 100, 1
INSERT INTO Inpours SELECT '李四', '2010-07-14', '支付宝', 100, 1
INSERT INTO Inpours SELECT '王五', '2010-07-14', '工商银行卡', 100, 1
INSERT INTO Inpours SELECT '赵六', '2010-07-14', '建设银行卡', 100, 1SELECT
CONVERT(VARCHAR(10), CreateTime, 120) AS CreateTime,
CASE PayType WHEN '支付宝' THEN SUM(Money) ELSE 0 END AS '支付宝',
CASE PayType WHEN '手机短信' THEN SUM(Money) ELSE 0 END AS '手机短信',
CASE PayType WHEN '工商银行卡' THEN SUM(Money) ELSE 0 END AS '工商银行卡',
CASE PayType WHEN '建设银行卡' THEN SUM(Money) ELSE 0 END AS '建设银行卡'
FROM Inpours
GROUP BY CreateTime, PayType
SELECT
CreateTime,
ISNULL(SUM([支付宝]) , 0) AS [支付宝],
ISNULL(SUM([手机短信]) , 0) AS [手机短信],
ISNULL(SUM([工商银行卡]), 0) AS [工商银行卡],
ISNULL(SUM([建设银行卡]), 0) AS [建设银行卡]
FROM
(
SELECT
CONVERT(VARCHAR(10), CreateTime, 120) AS CreateTime,
CASE PayType WHEN '支付宝' THEN SUM(Money) ELSE 0 END AS '支付宝' ,
CASE PayType WHEN '手机短信' THEN SUM(Money) ELSE 0 END AS '手机短信',
CASE PayType WHEN '工商银行卡' THEN SUM(Money) ELSE 0 END AS '工商银行卡',
CASE PayType WHEN '建设银行卡' THEN SUM(Money) ELSE 0 END AS '建设银行卡'
FROM Inpours
GROUP BY CreateTime, PayType
) T
GROUP BY CreateTimeDECLARE @cmdText VARCHAR(8000);
DECLARE @tmpSql VARCHAR(8000);
SET @cmdText = 'SELECT CONVERT(VARCHAR(10), CreateTime, 120) AS CreateTime,' + CHAR(10);
SELECT @cmdText = @cmdText + ' CASE PayType WHEN ''' +
PayType + ''' THEN SUM(Money) ELSE 0 END AS ''' + PayType
+ ''',' + CHAR(10) FROM (SELECT DISTINCT PayType FROM Inpours ) T
SET @cmdText = LEFT(@cmdText, LEN(@cmdText) -2) --注意这里，如果没有加CHAR(10) 则用LEFT(@cmdText, LEN(@cmdText) -1)
SET @cmdText = @cmdText + ' FROM Inpours
GROUP BY CreateTime, PayType ';
SET @tmpSql ='SELECT CreateTime,' + CHAR(10);
SELECT @tmpSql = @tmpSql + ' ISNULL(SUM(' + PayType + '), 0) AS ''' +
PayType + ''',' + CHAR(10)
FROM (SELECT DISTINCT PayType FROM Inpours ) T
SET @tmpSql = LEFT(@tmpSql, LEN(@tmpSql) -2) + ' FROM (' + CHAR(10);
SET @cmdText = @tmpSql + @cmdText + ') T GROUP BY CreateTime ';
PRINT @cmdText
EXECUTE (@cmdText);
SELECT CreateTime, [支付宝] , [手机短信],[工商银行卡] , [建设银行卡]
FROM
(
SELECT CONVERT(VARCHAR(10), CreateTime, 120) AS CreateTime,PayType, Money
FROM Inpours
) P
PIVOT (
SUM(Money)
FOR PayType IN
([支付宝], [手机短信], [工商银行卡], [建设银行卡])
) AS T
ORDER BY CreateTime有时可能会出现这样的错误：
消息 325，级别 15，状态 1，第 9 行
‘PIVOT’ 附近有语法错误。您可能需要将当前数据库的兼容级别设置为更高的值，以启用此功能。有关存储过程 sp_dbcmptlevel 的信息，请参见帮助。
这个是因为：对升级到 SQL Server 2005 或更高版本的数据库使用 PIVOT 和 UNPIVOT 时，必须将数据库的兼容级别设置为 90 或更高。有关如何设置数据库兼容级别的信息，请参阅 sp_dbcmptlevel (Transact-SQL)。例如，只需在执行上面脚本前加上 EXEC sp_dbcmptlevel Test, 90; 就OK了， Test 是所在数据库的名称。
下面我们来看看列转行，主要是通过UNION ALL ,MAX来实现。假如有下面这么一个表
Create Table ProgrectDetail
(
ProgrectName NVARCHAR(20), --工程名称
OverseaSupply INT, --海外供应商供给数量
NativeSupply INT, --国内供应商供给数量
SouthSupply INT, --南方供应商供给数量
NorthSupply INT --北方供应商供给数量
)
INSERT INTO ProgrectDetail
SELECT 'A', 100, 200, 50, 50
UNION ALL
SELECT 'B', 200, 300, 150, 150
UNION ALL
SELECT 'C', 159, 400, 20, 320
UNION ALL
SELECT 'D', 250, 30, 15, 15SELECT ProgrectName, 'OverseaSupply' AS Supplier,
MAX(OverseaSupply) AS 'SupplyNum'
FROM ProgrectDetail
GROUP BY ProgrectName
UNION ALL
SELECT ProgrectName, 'NativeSupply' AS Supplier,
MAX(NativeSupply) AS 'SupplyNum'
FROM ProgrectDetail
GROUP BY ProgrectName
UNION ALL
SELECT ProgrectName, 'SouthSupply' AS Supplier,
MAX(SouthSupply) AS 'SupplyNum'
FROM ProgrectDetail
GROUP BY ProgrectName
UNION ALL
SELECT ProgrectName, 'NorthSupply' AS Supplier,
MAX(NorthSupply) AS 'SupplyNum'
FROM ProgrectDetail
GROUP BY ProgrectName
用UNPIVOT 实现如下：
SELECT ProgrectName,Supplier,SupplyNum
FROM
(
SELECT ProgrectName, OverseaSupply, NativeSupply,
SouthSupply, NorthSupply
FROM ProgrectDetail
)T
UNPIVOT
(
SupplyNum FOR Supplier IN
(OverseaSupply, NativeSupply, SouthSupply, NorthSupply )
) P
