Question

有没有办法从SQL Server中的table A，table B或两个表中进行选择？尽可能多，我不想使用动态SQL。我在类似的question中看到了这一点，但它只在1个表格中选择。

Declare @table = 1

SELECT *
FROM Table1
WHERE <stuff>
AND @Table = 1

UNION ALL

SELECT *
FROM Table2
WHERE <stuff>
AND @Table = 2

Answer 1

你可以试试这个：

你有两个关于价值@table的解决方案。

您可以考虑@table = NULL关于两个表的选择，或者您可以考虑@table = value（例如3作为1和2的总和），所以你的查询变为：

如果选择@table = NULL：

Declare @table = NULL

SELECT *
FROM Table1
WHERE <stuff>
AND (@Table = 1 OR @table IS NULL)

UNION ALL

SELECT *
FROM Table2
WHERE <stuff>
AND (@Table = 2 OR @table IS NULL)

如果选择@Table = value（例如3）

Declare @table = 3

SELECT *
FROM Table1
WHERE <stuff>
AND (@Table = 1 OR @table = 3)

UNION ALL

SELECT *
FROM Table2
WHERE <stuff>
AND (@Table = 2 OR @table = 3)

Answer 2

您可以使用IF ... ELSE语句来实现此目的，如下所示。我假设您想使用@table来控制脚本应该做什么。

Declare @table = 1

IF @table = 1 
BEGIN
    SELECT *
    FROM Table1  
    WHERE <stuff>
END

ELSE IF @table = 2
BEGIN
    SELECT *
    FROM Table2
    WHERE <stuff>
END

ELSE IF @table = 3 /* OR @table IN (1,2) --depends on how you want to handle this*/
BEGIN
    SELECT *
    FROM Table1
    WHERE <stuff>

    UNION ALL

    SELECT *
    FROM Table2
    WHERE <stuff>
END

只要条件满足，脚本就会停止。例如，IF @Table = 2，只运行以下脚本部分：

ELSE IF @table = 2
BEGIN
    SELECT *
    FROM Table2
    WHERE <stuff>
END

Answer 3

希望这会有所帮助：

SELECT maker, Product.model AS model_1, PC.model AS model_2, price
FROM Product INNER JOIN PC ON PC.model = Product.model
ORDER BY maker, PC.model;

SQL Server：从tableA或tableB OR Both中选择

3 个答案: