PostgreSQL的：在UPDATE

Question

不能使用聚合函數我有我移植到PostgreSQL的Oracle查詢：

UPDATE "SPD_PG"."TT_SPLDR_11A2F324_29" 
SET "SECT_ORDER" = MAX("SECTIONS"."SECT_ORDER")+1 FROM "SPD_PG"."SECTIONS" 
INNER JOIN "SPD_PG"."META_SECTIONS" ON ("SECTIONS"."META_SECT_ID"="META_SECTIONS"."META_SECT_ID") 
WHERE ("META_SECTIONS"."META_SECT_ORDER"="TT_SPLDR_11A2F324_29"."META_SECT_ORDER"-1) 
AND ("SECTIONS"."DOC_ID"="TT_SPLDR_11A2F324_29"."DOC_ID") 
AND ("TT_SPLDR_11A2F324_29"."META_SECT_ORDER">0) 

這給我：ERROR: cannot use aggregate function in UPDATE，似乎PostgreSQL不支持MAX在Update語句。

但是如果我重寫查詢如下：

UPDATE "SPD_PG"."TT_SPLDR_11A2F324_29" 
SET "SECT_ORDER" = "MAX_VALUE" FROM (
    SELECT MAX("SECTIONS"."SECT_ORDER")+1 AS "MAX_VALUE" FROM "SPD_PG"."SECTIONS" 
    INNER JOIN "SPD_PG"."META_SECTIONS" ON ("SECTIONS"."META_SECT_ID"="META_SECTIONS"."META_SECT_ID") 
    WHERE ("META_SECTIONS"."META_SECT_ORDER"="TT_SPLDR_11A2F324_29"."META_SECT_ORDER"-1) 
    AND ("SECTIONS"."DOC_ID"="TT_SPLDR_11A2F324_29"."DOC_ID") 
    AND ("TT_SPLDR_11A2F324_29"."META_SECT_ORDER">0) 
) "TBL_ALIAS" 

它說ERROR: subquery in FROM cannot refer to other relations of same query level。

所以我想不出如何編寫這個查詢。

Answer 1

試試這個：

UPDATE "SPD_PG"."TT_SPLDR_11A2F324_29" 
    SET "SECT_ORDER" = (SELECT MAX("SECTIONS"."SECT_ORDER")+1 
         FROM "SPD_PG"."SECTIONS" 
         INNER JOIN "SPD_PG"."META_SECTIONS" ON ("SECTIONS"."META_SECT_ID"="META_SECTIONS"."META_SECT_ID") 
         WHERE ("META_SECTIONS"."META_SECT_ORDER"="TT_SPLDR_11A2F324_29"."META_SECT_ORDER"-1) 
          AND ("SECTIONS"."DOC_ID"="TT_SPLDR_11A2F324_29"."DOC_ID") 
          AND ("TT_SPLDR_11A2F324_29"."META_SECT_ORDER">0) 
        )