1.問題說明

項目有兩個不同的平臺分別使用 Greenplum 和 MySQL 數據庫，但是這兩個數據庫的函數是不相同的，所以需要維護兩套查詢 SQL。

2.根據周幾獲取數據

2.1 原始函數結果

MySQL獲取周幾的函數為date_format( date, '%w')結果是周一到周日為：1，2，3，4，5，6，0

-- MySQL數據庫 SELECT '周一' AS weekInfo, date_format( '2022-04-11 08:00:00', '%w') AS weekVal UNION ALL SELECT '周二' AS weekInfo, date_format( '2022-04-12 08:00:00', '%w') AS weekVal UNION ALL SELECT '周三' AS weekInfo, date_format( '2022-04-13 08:00:00', '%w') AS weekVal UNION ALL SELECT '周四' AS weekInfo, date_format( '2022-04-14 08:00:00', '%w') AS weekVal UNION ALL SELECT '周五' AS weekInfo, date_format( '2022-04-15 08:00:00', '%w') AS weekVal UNION ALL SELECT '周六' AS weekInfo, date_format( '2022-04-16 08:00:00', '%w') AS weekVal UNION ALL SELECT '周日' AS weekInfo, date_format( '2022-04-17 08:00:00', '%w') AS weekVal

Greenplum獲取周幾的函數為to_char( timestamp, 'd')結果是周一到周日為：2，3，4，5，6，1

-- Greenplum數據庫 SELECT '周一' AS weekInfo, to_char( to_timestamp( '2022-04-11 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS weekVal UNION ALL SELECT '周二' AS weekInfo, to_char( to_timestamp( '2022-04-12 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS weekVal UNION ALL SELECT '周三' AS weekInfo, to_char( to_timestamp( '2022-04-13 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS weekVal UNION ALL SELECT '周四' AS weekInfo, to_char( to_timestamp( '2022-04-14 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS weekVal UNION ALL SELECT '周五' AS weekInfo, to_char( to_timestamp( '2022-04-15 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS weekVal UNION ALL SELECT '周六' AS weekInfo, to_char( to_timestamp( '2022-04-16 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS weekVal UNION ALL SELECT '周日' AS weekInfo, to_char( to_timestamp( '2022-04-17 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS weekVal

2.2 實現函數結果一致

可以看到 MySQL 的函數獲取的結果是數值，將結果+1即可實現與 Greenplum 數據庫函數結果一致。

-- MySQL數據庫 SELECT '周一' AS weekInfo, date_format( '2022-04-11 08:00:00', '%w') +1 AS weekVal UNION ALL SELECT '周二' AS weekInfo, date_format( '2022-04-12 08:00:00', '%w') +1 AS weekVal UNION ALL SELECT '周三' AS weekInfo, date_format( '2022-04-13 08:00:00', '%w') +1 AS weekVal UNION ALL SELECT '周四' AS weekInfo, date_format( '2022-04-14 08:00:00', '%w') +1 AS weekVal UNION ALL SELECT '周五' AS weekInfo, date_format( '2022-04-15 08:00:00', '%w') +1 AS weekVal UNION ALL SELECT '周六' AS weekInfo, date_format( '2022-04-16 08:00:00', '%w') +1 AS weekVal UNION ALL SELECT '周日' AS weekInfo, date_format( '2022-04-17 08:00:00', '%w') +1 AS weekVal

Greenplum 的函數獲取的結果是字符，需要將結果轉換成數值再-1即可實現與 MySQL 數據庫函數結果一致。

-- Greenplum數據庫 SELECT '周一' AS weekInfo, cast( to_char( to_timestamp( '2022-04-11 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS int) -1 AS weekVal UNION ALL SELECT '周二' AS weekInfo, cast( to_char( to_timestamp( '2022-04-12 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS int) -1 AS weekVal UNION ALL SELECT '周三' AS weekInfo, cast( to_char( to_timestamp( '2022-04-13 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS int) -1 AS weekVal UNION ALL SELECT '周四' AS weekInfo, cast( to_char( to_timestamp( '2022-04-14 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS int) -1 AS weekVal UNION ALL SELECT '周五' AS weekInfo, cast( to_char( to_timestamp( '2022-04-15 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS int) -1 AS weekVal UNION ALL SELECT '周六' AS weekInfo, cast( to_char( to_timestamp( '2022-04-16 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS int) -1 AS weekVal UNION ALL SELECT '周日' AS weekInfo, cast( to_char( to_timestamp( '2022-04-17 08:00:00', 'YYYY-MM-DD hh24:mi:ss' ), 'd' ) AS int) -1 AS weekVal

兩種方式選擇一種即可。

總結

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