postgres查詢沒有結果數據的目的地

Question

我對pgSQL很陌生。

任何人都可以幫助解決這個錯誤？

ERROR: query has no destination for result data 
HINT: If you want to discard the results of a SELECT, use PERFORM instead. 
CONTEXT: PL/pgSQL function prac_data.document_get_document_title(integer) line 8 at SQL statement 

的腳本...

CREATE OR REPLACE FUNCTION prac_data.document_get_document_title(documentid INTEGER) RETURNS TEXT 
AS 
$body$ 
DECLARE 
xmlText XML; 
rawText TEXT; 
BEGIN 
    SELECT document into STRICT rawText FROM prac_data.document_table WHERE entity_id = documentid; 
    xmlText := XMLParse (DOCUMENT rawText);    
    SELECT xpath('/inps_flow_document/@title', xmlText) as titleText; 
    RETURN titleText; 
    EXCEPTION 
    WHEN NO_DATA_FOUND THEN 
      RAISE EXCEPTION 'document_id % not found', documentid; 
END; 
$body$ LANGUAGE PLPGSQL; 


SELECT prac_data.document_get_document_title(1) 

IM使用SELECT INTO（可被看到的），但也許我不使用它完全正確....

Answer 1

嘗試類似於：

CREATE OR REPLACE FUNCTION prac_data.document_get_document_title(documentid INTEGER) RETURNS TEXT 
AS 
$body$ 
DECLARE 
xmlText XML; 
rawText TEXT; 
titleText TEXT; 
BEGIN 
    SELECT document into STRICT rawText FROM prac_data.document_table WHERE entity_id = documentid; 
    xmlText := XMLParse (DOCUMENT rawText);    
    titleText := xpath('/inps_flow_document/@title', xmlText); 
    RETURN titleText; 
    EXCEPTION 
    WHEN NO_DATA_FOUND THEN 
      RAISE EXCEPTION 'document_id % not found', documentid; 
END; 
$body$ LANGUAGE PLPGSQL;