验证条件后插入 2 行

Question

我有一个 SELECT INTO #tTable SELECT CASE WHEN 条件 THEN value1 ELSE value2 查询。 验证特定条件后，我必须插入 #tTable 2 行而不是 1 行，它们仅在 1 列中彼此不同。

我是这样解决这个问题的：

1. 在 #tTable 中插入一个 foo 行，其中包含我的列 v1v2 的值

2. 插入#tTable value1 where col = v1v2

3. 插入#tTable value2 where col = v1v2

4. 从 #tTable 中删除，其中 col = v1v2

有没有更好、性能更高的方法来做到这一点？有没有办法在 INSERT INTO #table SELECT CASE WHEN 语句中插入 2 行？

例子：

INSERT INTO #tTable (col1, col2, col3)

SELECT T.col1, T.col2, CASE WHEN T.col1 > T.col2 THEN v1v2

WHEN T.col1 = T.col2 THEN value1 ELSE value2 END

FROM Table1 as T;

INSERT INTO #tTable (col1, col2, col3)

SELECT T.col1, T.col2, value1

FROM Table1 as T

WHERE T.col3 = v1v2;

INSERT INTO #tTable (col1, col2, col3)

SELECT T.col1, T.col2, value2

FROM Table1 as T

WHERE T.col3 = v1v2;

DELETE FROM #tTable

WHERE col3 = v1v2;

当 T.col1 > T.col2 时，我必须插入 2 行（一行带有 value1，另一行带有 value2）

编辑：

其实我的查询是这样的：

INSERT INTO #tTable (col1, col2, col3)

SELECT T.col1, T.col2,

CASE WHEN condition1 AND condition2 AND condition3 THEN value1

WHEN condition4 AND condition5 AND condition6 THEN value2

WHEN condition7 AND condition8 AND condition9 THEN v1v2 END

FROM Table1 as T

Answer 1

您不能使用CASE 生成另一行，您必须使用UNION ALL 或额外的INSERT。我看到的最简单的方法是使用UNION ALL，在每个SELECT 上重复v1 + v2 的条件：

INSERT INTO #tTable (
    col1, 
    col2, 
    col3)
SELECT
    V.Col1,
    V.Col2,
    col3 = V.value1
FROM
    Table1 AS V
WHERE
    (condition1 AND condition2 AND condition3) OR -- value1 condition
    (condition7 AND condition8 AND condition9) -- shared condition

UNION ALL

SELECT
    V.Col1,
    V.Col2,
    col3 = V.value2
FROM
    Table1 AS V
WHERE
    (condition4 AND condition5 AND condition6) OR -- value2 condition
    (condition7 AND condition8 AND condition9) -- shared condition

如果您的条件必然会发生变化或很复杂，则只需将它们放在 CTE 上并引用它们的输出即可编写一次：

;WITH DataWithConditions AS
(
    SELECT
        T.Col1,
        T.Col2,
        T.Value1,
        T.Value2,
        Condition = CASE
            WHEN condition1 AND condition2 AND condition3 THEN 1
            WHEN condition4 AND condition5 AND condition6 THEN 2
            WHEN condition7 AND condition8 AND condition9 THEN 3 END
    FROM
        Table1 AS T
)
INSERT INTO #tTable (
    col1, 
    col2, 
    col3)
SELECT
    V.Col1,
    V.Col2,
    col3 = V.value1
FROM
    DataWithConditions AS V
WHERE
    V.Condition IN (1, 3)

UNION ALL

SELECT
    V.Col1,
    V.Col2,
    col3 = V.value2
FROM
    DataWithConditions AS V
WHERE
    V.Condition IN (2, 3)

Answer 2

您可以尝试 UNION ALL 将第二列的值合并为 ROW，如下所示-

INSERT INTO #tTable (col1, col2, col3)

SELECT T.col1, T.col2,
       CASE
           WHEN T.col1 > T.col2 THEN value1 -- Column name may be v1v2
           WHEN T.col1 = T.col2 THEN value1
           ELSE value2
       END
FROM Table1 AS T

UNION ALL

SELECT T.col1, T.col2,value2 -- Value2 I guess the 2nd column
FROM Table1 AS T WHERE  T.col1 > T.col2