WITH final AS (    SELECT 'a' AS gname, 'b' AS pname, 'c' AS name, 1 AS gid, 2 AS pid, 3 AS did, 3 AS inp    UNION    SELECT 'a1' AS gname, 'b1' AS pname, 'c1' AS name, 11 AS gid, 21 AS pid, 31 AS did, 3 AS inp)現在我想根據 inp 列值編寫一個查詢SELECT     (CASE final.inp     WHEN 1        THEN         (SELECT DISTINCT(final.gid) AS id, final.gname as name FROM        final ORDER BY final.gname)    WHEN 2        THEN         (SELECT DISTINCT(final.pid) AS id, final.pname as name FROM        final WHERE final.gid = $1 ORDER BY final.pname)    WHEN 3         THEN         (SELECT DISTINCT(final.did) AS id, final.name as name FROM        final WHERE final.pid = $1 ORDER BY final.name)    END)        FROM (%s) final;我知道這不是正確的寫法。但這會讓您了解我正在嘗試做什么。if inp = 1-> 獲取唯一的 gid 和 gname 并按 gname 排序如果inp = 2-> 獲取唯一的 pid 和 pname，其中 gid = 并按 pname 排序。我想在 psql 中編寫這個邏輯。我知道案例When只能有一列，所以我必須final.inp=1為名稱和 ID 創建兩個案例。由于這部分，我無法編寫此邏輯(SELECT DISTINCT(final.pid) AS id, final.pname as name FROMfinal WHERE final.gid = $1 ORDER BY final.pname) WHERE ORDER BY<--- 并將相同的最終值傳遞給它。我無法實施它。誰能幫忙？