Microsoft SQL Server 简单的PIVOT和UNPIVOT(T-SQL)
示例
以下是一个简单的示例，显示了每个工作日每个项目的平均价格。
首先，假设我们有一个表格，其中每天记录着所有物品的价格。
CREATE TABLE tbl_stock(item NVARCHAR(10), weekday NVARCHAR(10), price INT);
INSERT INTO tbl_stock VALUES
('Item1', 'Mon', 110), ('Item2', 'Mon', 230), ('Item3', 'Mon', 150),
('Item1', 'Tue', 115), ('Item2', 'Tue', 231), ('Item3', 'Tue', 162),
('Item1', 'Wed', 110), ('Item2', 'Wed', 240), ('Item3', 'Wed', 162),
('Item1', 'Thu', 109), ('Item2', 'Thu', 228), ('Item3', 'Thu', 145),
('Item1', 'Fri', 120), ('Item2', 'Fri', 210), ('Item3', 'Fri', 125),
('Item1', 'Mon', 122), ('Item2', 'Mon', 225), ('Item3', 'Mon', 140),
('Item1', 'Tue', 110), ('Item2', 'Tue', 235), ('Item3', 'Tue', 154),
('Item1', 'Wed', 125), ('Item2', 'Wed', 220), ('Item3', 'Wed', 142);该表应如下所示：
+========+=========+=======+ | item | weekday | price | +========+=========+=======+ | Item1 | Mon | 110 | +--------+---------+-------+ | Item2 | Mon | 230 | +--------+---------+-------+ | Item3 | Mon | 150 | +--------+---------+-------+ | Item1 | Tue | 115 | +--------+---------+-------+ | Item2 | Tue | 231 | +--------+---------+-------+ | Item3 | Tue | 162 | +--------+---------+-------+ | . . . | +--------+---------+-------+ | Item2 | Wed | 220 | +--------+---------+-------+ | Item3 | Wed | 142 | +--------+---------+-------+
为了执行汇总以查找每个工作日的平均价格，我们将使用关系运算符PIVOT将weekday表值表达式的列旋转为汇总行值，如下所示：
SELECT * FROM tbl_stock
PIVOT (
AVG(price) FOR weekday IN ([Mon], [Tue], [Wed], [Thu], [Fri])
) pvt;结果：
+--------+------+------+------+------+------+ | item | Mon | Tue | Wed | Thu | Fri | +--------+------+------+------+------+------+ | Item1 | 116 | 112 | 117 | 109 | 120 | | Item2 | 227 | 233 | 230 | 228 | 210 | | Item3 | 145 | 158 | 152 | 145 | 125 | +--------+------+------+------+------+------+
最后，为了执行的反向操作PIVOT，我们可以使用关系运算符UNPIVOT将列旋转为行，如下所示：
SELECT * FROM tbl_stock
PIVOT (
AVG(price) FOR weekday IN ([Mon], [Tue], [Wed], [Thu], [Fri])
) pvt
UNPIVOT (
price FOR weekday IN ([Mon], [Tue], [Wed], [Thu], [Fri])
) unpvt;结果：
+=======+========+=========+ | item | price | weekday | +=======+========+=========+ | Item1 | 116 | Mon | +-------+--------+---------+ | Item1 | 112 | Tue | +-------+--------+---------+ | Item1 | 117 | Wed | +-------+--------+---------+ | Item1 | 109 | Thu | +-------+--------+---------+ | Item1 | 120 | Fri | +-------+--------+---------+ | Item2 | 227 | Mon | +-------+--------+---------+ | Item2 | 233 | Tue | +-------+--------+---------+ | Item2 | 230 | Wed | +-------+--------+---------+ | Item2 | 228 | Thu | +-------+--------+---------+ | Item2 | 210 | Fri | +-------+--------+---------+ | Item3 | 145 | Mon | +-------+--------+---------+ | Item3 | 158 | Tue | +-------+--------+---------+ | Item3 | 152 | Wed | +-------+--------+---------+ | Item3 | 145 | Thu | +-------+--------+---------+ | Item3 | 125 | Fri | +-------+--------+---------+