将 SQL Server 查询重写为 postgresql 并将 stuff() 替换为 string_agg() 时出错

Question

我正在将应用程序从 SQL Server 迁移到 Postgresql，并且必须重写一些定期运行的查询。特别是我遇到了麻烦，因为我必须用string_agg() 替换stuff() 和XML Path。通常我可以这样做，但在这种情况下，stuff() 是一个子查询，所以当我运行它时，我收到一个“由用作表达式的子查询返回的多行”错误。我对 SQL 和 Postgresql 的经验还不够丰富，无法解决这个问题。

我遇到困难的 SQL Server 部分：

SELECT P.pkey + '-' + CAST(JI.issuenum AS VARCHAR(18)) [CASE NUMBER]
, IT.pname [ISSUE TYPE (PREVIOUSLY CASE REASON)]
, JI.CREATED [OPENED DATE]
, CRE.display_name [CREATOR]
, DEP.BIG_DATA [DEPARTMENT]
, REG.BIG_DATA [OFFICE]
, JI.RESOLUTIONDATE [CLOSED DATE]
, STUFF((     SELECT CAST(', ' + COM.cname AS VARCHAR(MAX))
                     FROM nodeassociation NAC
                     INNER JOIN component COM ON NAC.SINK_NODE_ID = COM.ID
                     WHERE NAC.SOURCE_NODE_ID = JI.ID
                     ORDER BY COM.cname
                     FOR XML PATH('')), 1, 2, '') [COMPONENT(S)]
, RCS.customvalue [RESOLUTION CODE (SERVICE)]
, ISNULL(RCI1.customvalue + ' - ', '') + RCI2.customvalue [RESOLTUION CODE (INCIDENT)]
, ISNULL(RCMT1.customvalue + ' - ', '') + ISNULL(RCMT2.customvalue + ' - ','') + ISNULL(RCMT3.customvalue,'') [RESOLTUION CODE (3-tier)]

我失败的 postgres 重写返回错误：

用作表达式的子查询返回多于一行

SELECT P.pkey || '-' || CAST(JI.issuenum AS VARCHAR(18)) AS "CASE NUMBER"
, IT.pname "ISSUE TYPE (PREVIOUSLY CASE REASON)"
, JI.CREATED "OPENED DATE"
, CRE.display_name "CREATOR"
, JI.RESOLUTIONDATE "CLOSED DATE"
, string_agg((SELECT COM.cname 
                     FROM nodeassociation NAC
                     INNER JOIN component COM ON NAC.SINK_NODE_ID = COM.ID
                     WHERE NAC.SOURCE_NODE_ID = JI.ID
                     ORDER BY COM.cname, p.pkey, JI.issuenum, IT.pname, JI.CREATED, CRE.display_name, JI.RESOLUTIONDATE, RCS.customvalue, RCI1.customvalue, RCI2.customvalue, RCMT1.customvalue, RCMT2.customvalue, RCMT3.customvalue, DEP."BIG_DATA", REG."BIG_DATA" 
                     ), '') AS COMPONENTS
, RCS.customvalue RESOLUTION_CODE_SERVICE
, coalesce(RCI1.customvalue || ' - ', '') || RCI2.customvalue "RESOLTUION-CODE-INCIDENT"
, coalesce(RCMT1.customvalue || ' - ', '') || coalesce(RCMT2.customvalue || ' - ','') || coalesce(RCMT3.customvalue,'') "RESOLTUION-CODE 3-tier"
, DEP."BIG_DATA" "DEPARTMENT"
, REG."BIG_DATA" "OFFICE"

我使用过这个old post 来将stuff() 替换为string_agg()，但它不包括子查询。

Answer 1

尝试替换这个：

string_agg((SELECT COM.cname 
                     FROM nodeassociation NAC
                     INNER JOIN component COM ON NAC.SINK_NODE_ID = COM.ID
                     WHERE NAC.SOURCE_NODE_ID = JI.ID
                     ORDER BY COM.cname, p.pkey, JI.issuenum, IT.pname, JI.CREATED, CRE.display_name, JI.RESOLUTIONDATE, RCS.customvalue, RCI1.customvalue, RCI2.customvalue, RCMT1.customvalue, RCMT2.customvalue, RCMT3.customvalue, DEP."BIG_DATA", REG."BIG_DATA" 
                     ), '') AS COMPONENTS

关于这个：

(SELECT string_agg(COM.cname,'')
                     FROM nodeassociation NAC
                     INNER JOIN component COM ON NAC.SINK_NODE_ID = COM.ID
                     WHERE NAC.SOURCE_NODE_ID = JI.ID
                     ORDER BY COM.cname, p.pkey, JI.issuenum, IT.pname, JI.CREATED, CRE.display_name, JI.RESOLUTIONDATE, RCS.customvalue, RCI1.customvalue, RCI2.customvalue, RCMT1.customvalue, RCMT2.customvalue, RCMT3.customvalue, DEP."BIG_DATA", REG."BIG_DATA" 
                     ) AS COMPONENTS