我想排除不屬於 case when 語句中指定的值範圍的記錄 - SQL/MySQL

Question

我正在嘗試為來自 DTBL_SCHOOL_DATES 表的特定日期設定季節範圍。以下是我的邏輯，它根據年份及其地區來設定給定範圍內的季節。

CASE 
        WHEN RTRIM(dtbl_school_dates.local_school_year) = '2021-2022' THEN 
            CASE 
                WHEN RTRIM(dtbl_schools_ext.region) = 'Bay Area' AND 
                    CAST(dtbl_school_dates.date_value AS DATE) BETWEEN '08/07/2021' and '09/08/2021' THEN 'FALL'
                WHEN RTRIM(dtbl_schools_ext.region) = 'Bay Area' AND 
                    CAST(dtbl_school_dates.date_value AS DATE) BETWEEN '11/27/2021' and '12/15/2021' THEN 'WINTER'
                WHEN RTRIM(dtbl_schools_ext.region) = 'Bay Area' AND 
                    CAST(dtbl_school_dates.date_value AS DATE) BETWEEN '03/04/2022' and '03/22/2022' THEN 'SPRING'
                WHEN RTRIM(dtbl_schools_ext.region) = 'Central Valley' AND 
                    CAST(dtbl_school_dates.date_value AS DATE) BETWEEN '07/31/2021' and '09/01/2021' THEN 'FALL'
                WHEN RTRIM(dtbl_schools_ext.region) = 'Central Valley' AND 
                    CAST(dtbl_school_dates.date_value AS DATE) BETWEEN '11/27/2021' and '12/15/2021' THEN 'WINTER'
                WHEN RTRIM(dtbl_schools_ext.region) = 'Central Valley' AND 
                    CAST(dtbl_school_dates.date_value AS DATE) BETWEEN '02/19/2022' and '03/08/2022' THEN 'SPRING'
                WHEN RTRIM(dtbl_schools_ext.region) = 'Los Angeles' AND 
                    CAST(dtbl_school_dates.date_value AS DATE) BETWEEN '08/14/2021' and '09/15/2021' THEN 'FALL'
                WHEN RTRIM(dtbl_schools_ext.region) = 'Los Angeles' AND 
                    CAST(dtbl_school_dates.date_value AS DATE) BETWEEN '11/27/2021' and '12/15/2021' THEN 'WINTER'
                WHEN RTRIM(dtbl_schools_ext.region) = 'Los Angeles' AND 
                    CAST(dtbl_school_dates.date_value AS DATE) BETWEEN '03/04/2022' and '03/22/2022' THEN 'SPRING' 
                ELSE 'NOT IN RANGE' 
            END 
        ELSE FTBL_TEST_SCORES.test_admin_period 
    END AS "C4630"

但是每當日期不在邏輯中指定的範圍內時，我希望它們被忽略。又稱為“不在範圍內”的值應該被排除。我嘗試使用 FTBL_TEST_SCORES.test_admin_period 不為空，並且由於資料庫中沒有值為空，它們將無法運作。

不在範圍內的值應該被排除在結果中，我如何在 where 子句中實現這一點

我嘗試使用 Alias 進行限制，但不起作用。 我不確定是否可以將值分配給 case 語句中的特定字段，例如 Case when 'a' then field ='B' end

不在範圍內的值應該被排除在結果中，我如何在 where 子句中實現這一點

Answer 1

如果無法查看完整的查詢，就不可能提出最佳解決方案。最簡單的解決方案是將標準新增為 HAVING 子句：

HAVING `C4630` <> 'NOT IN RANGE'

我對你的日期格式感到困惑。如果這應該是 MySQL 查詢，則它們應該採用 yyyy-mm-dd 格式。可以說，即使在支援不明確的本機日期格式的 SQL Server 上，它們也應該採用這種格式。

為什麼都是RTRIM和CAST？數據應該以正確的格式存儲，並在輸入時進行清理，如果無法做到這一點，請定期清理數據，而不是對每個查詢進行清理。

明智的做法是將您的季節移動到它們自己的表中，而不是在查詢時定義它們。然後它是一個簡單的連接到seasons。我在這裡使用了子查詢，但希望您能明白：

SELECT
    /* other columns */
    COALESCE(seasons.season, FTBL_TEST_SCORES.test_admin_period) AS `C4630`
FROM all_the_other_tables
LEFT JOIN (

    SELECT 'Bay Area' AS region, 'FALL' AS season, '2021-08-07' AS start, '2021-09-08' AS end UNION ALL
    SELECT 'Bay Area'          , 'WINTER'        , '2021-11-27'         , '2021-12-15'        UNION ALL
    SELECT 'Bay Area'          , 'SPRING'        , '2022-03-04'         , '2022-03-22'        UNION ALL
        
    SELECT 'Central Valley'    , 'FALL'          , '2021-07-31'         , '2021-09-01'        UNION ALL
    SELECT 'Central Valley'    , 'WINTER'        , '2021-11-27'         , '2021-12-15'        UNION ALL
    SELECT 'Central Valley'    , 'SPRING'        , '2022-02-19'         , '2022-03-08'        UNION ALL
        
    SELECT 'Los Angeles'       , 'FALL'          , '2021-08-14'         , '2021-09-15'        UNION ALL
    SELECT 'Los Angeles'       , 'WINTER'        , '2021-11-27'         , '2021-12-15'        UNION ALL
    SELECT 'Los Angeles'       , 'SPRING'        , '2022-03-04'         , '2022-03-22'

) AS seasons
    ON dtbl_school_dates.local_school_year = '2021-2022'
    AND dtbl_schools_ext.region = seasons.region
    AND dtbl_school_dates.date_value BETWEEN seasons.start AND seasons.end
WHERE (
    (dtbl_school_dates.local_school_year = '2021-2022' AND seasons.season IS NOT NULL) OR
    dtbl_school_dates.local_school_year <> '2021-2022'
);

Answer 2

您可以在 WHERE 子句中重複整個 CASE 語句，如下所示：

select
    case
        when x then y 
        when a then b 
        when c then d 
        else 'NOT IN RANGE'
    end as foo
from
    table t 
where 
    case
        when x then y 
        when a then b 
        when c then d 
        else 'NOT IN RANGE'
    end <> 'NOT IN RANGE'

或您可以使用子查詢（或 CTE），如下所示：

select * 
from (
    select
        case
            when x then y 
            when a then b 
            when c then d 
            else 'NOT IN RANGE'
        end as foo
    from
        table t 
) 
where foo <> 'NOT IN RANGE'