Question

我有两个桌子。满足条件时，我想更新table1。这里的条件是检查table 2中的国家，如果是Mex，则将比率0.5乘以price。

我写了以下代码

UPDATE table1
SET table1.Price = (SELECT *,
                           CASE table2.Country
                                WHEN 'CANADA' THEN (1 * table2.price)
                                WHEN 'MEXICO' THEN (0.5 * table2.price)
                                ELSE 0
                           END AS Price_Calc
                    FROM table2)
FROM table1;

运行此命令会出现以下错误

信息116，级别16，状态1，第12行
只能有一个表达式未在子查询中引入子查询时在选择列表中指定存在。

Answer 1

尝试如下

UPDATE t1
SET t1.table1.Price = (SELECT
                           CASE t2.Country
                                WHEN 'CANADA' THEN (1 * t2.price)
                                WHEN 'MEXICO' THEN (0.5 * t2.price)
                                ELSE 0
                           END AS Price_Calc
                    FROM table2 t2
                    WHERE t2.Id = t1.Id -- Here it is suggestion to update target 
                                        -- column based on relation if exists between 
                                        -- ur  tables

                     )
FROM table1 t1;

Answer 2

假设Table1和Table2通过ID相关联：

UPDATE t1 SET t1.Price = t2.Price 
                    * CASE t2.Country 
                        WHEN 'CANADA' THEN 1. 
                        WHEN 'MEXICO' THEN .5
                        ELSE 0
                      END
FROM table1 t1
INNER JOIN table2 t2 ON t2.Id = t1.Id
;

用多个表更新用例

2 个答案: