PostgreSql：不能在 UPDATE 中使用聚合函数

Question

我有一个移植到 PostgreSql 的 Oracle 查询：

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)

这给我：ERROR: cannot use aggregate function in UPDATE，好像 PostgreSql 不支持更新语句中的MAX。

但是，如果我将查询重写如下：

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"

上面写着ERROR: subquery in FROM cannot refer to other relations of same query level。

所以我不知道如何编写这个查询。

Answer 1

试试这个：

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)
                      )