Question

我必须编写SQL语句来切换CompanyName中table1的值，以便当前具有值'Linens and Things'的所有行都具有值'Lamps and Lighting'，并且所有当前具有值'Lamps and Lighting'的行将具有值'Linens and Things'。

我的表目前看起来像这样：

id  CompanyName
--- ----------------------
1   'Linens and Things'
2   'Linens and Things'
3   'Lamps and Lighting'
4   'Lamps and Lighting'
5   'A Different Vendor'

更新后，它应如下所示：

id  CompanyName
--- ----------------------
1   'Lamps and Lighting'
2   'Lamps and Lighting'
3   'Linens and Things'
4   'Linens and Things'
5   'A Different Vendor'

Answer 1

不确定这是你想要的：

UPDATE table1
SET CompanyName = CASE WHEN CompanyName = 'Linens and Things' THEN 'Lamps and Lighting'
                       WHEN CompanyName = 'Lamps and Lighting' THEN 'Linens and Things'
                       ELSE CompanyName
                       END
WHERE CompanyName IN ('Linens and Things','Lamps and Lighting')

Answer 2

当您反转这些值时，您需要按照以下步骤进行3次不同的更新（3个步骤）;

步骤1：更改现有“亚麻布和物品”的值;

Update table1 set CompanyName = "x"
where  CompanyName = "Linens and Things"

步骤2：将供应商的灯具和灯具'修改为'亚麻布和物品';

Update table1 set CompanyName = "Linens and Things"
where  CompanyName = "Lamps and Lighting"

步骤3：将最初“亚麻布和东西”的供应商修改为“灯具和灯具”;

Update table1 set CompanyName = "Lamps and Lighting"
where  CompanyName = "x"

Answer 3

T-SQL UPDATE语句有一个FROM子句，可以在更新表之前计算表。对于这种情况，我们可以将新名称计算为AlternateCompanyName并设置CompanyName=AlternateCompanyName。

UPDATE table1
SET CompanyName = ComputedTable.AlternateCompanyName
FROM (
    SELECT
        id,
        CompanyName,
        CASE
          WHEN CompanyName = 'Linens and Things' THEN 'Lamps and Lighting'
          WHEN CompanyName = 'Lamps and Lighting' THEN 'Linens and Things'
        END AS AlternateCompanyName
    FROM table1
) AS ComputedTable
JOIN table1 ON table1.id = ComputedTable.id
WHERE table1.CompanyName IN ('Lamps and Lighting', 'Linens and Things')

如何编写SQL UPDATE语句同时更新？

3 个答案: