【DM版本】:DM Database Server 64 V8
【操作系统】：window10
【CPU】:AMD A8-7680 Radeon R7, 10 Compute Cores 4C+6G 3.50 GHz
【问题描述】：

1. sql用例

-- 报错用例
WITH test_data AS (
    SELECT 1 AS id, 100 AS num_value
)
SELECT CASE WHEN COALESCE(MAX(num_value), '') IS NULL THEN 0 ELSE MAX(num_value) END
FROM test_data
GROUP BY id;

-- 不报错对照用例
WITH test_data AS (
    SELECT 1 AS id, 100 AS num_value
    UNION ALL
    SELECT 1 AS id, 200 AS num_value
)
SELECT CASE WHEN COALESCE(MAX(num_value), '') IS NULL THEN 0 ELSE MAX(num_value) END
FROM test_data
GROUP BY id;

2. 实际结果

单行CTE报错-4083"引用列未找到"
多行CTE执行成功

3. 预期结果

正常执行，或
返回明确的数据类型错误

4. 影响分析

导致应用代码在不改变SQL的情况下，因数据量变化而意外失败
影响查询的稳定性和可预测性