Question

如果我将这两个Postgres函数定义保存在两个单独的.sql文件中：

CREATE OR REPLACE FUNCTION column_exists(tablename text, colname text) RETURNS boolean AS 
        $BODY$
        DECLARE
            q text;
            field_name text;
            onerow record;
        BEGIN
            q = 'SELECT column_name FROM information_schema.columns WHERE table_name='''||tablename||''' AND table_schema =''public''';
            FOR onerow IN EXECUTE q
                LOOP
                   field_name := onerow.column_name;
                   IF ((field_name = colname)) then
                    RETURN true;
                   END IF;                  
                END LOOP;
            RETURN false;
        END;
    $BODY$
LANGUAGE plpgsql
CREATE OR REPLACE FUNCTION correct_col_names() RETURNS VOID AS
    $BODY$
        DECLARE
            q boolean;
        BEGIN                       

             -- rename name column to Name
             select column_exists('National_Parks', 'name') as q;
             IF q = TRUE THEN
            alter table "National_Parks"
            rename column name to "Name";
             END IF;    

             -- remance descriptio column to description
             select column_exists('National_Parks', 'descriptio') as q;
             IF q = TRUE THEN
            alter table "Natioanl_Parks"
            rename column descriptio to "Description";
             END IF;    

        END
    $BODY$
LANGUAGE plpgsql

我需要使用什么语法来调用顺序，比如在另一个脚本中？我试过了

select correct_col_names()

并返回以下错误：

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 "correct_col_names" line 7 at SQL statement

********** Error **********

ERROR: query has no destination for result data
SQL state: 42601
Hint: If you want to discard the results of a SELECT, use PERFORM instead.
Context: PL/pgSQL function "correct_col_names" line 7 at SQL statement

TIA。

Answer 1

问题是你有SELECT语句没有对数据做任何事情。你的

select column_exists('National_Parks', 'name') as q;

应该是

select column_exists('National_Parks', 'name') INTO q;

as只是将结果别名为该查询的“q”，它实际上并没有将它放入q变量。

调用函数（select correct_col_names()）的语法对于SQL是正确的。一旦你修复了该函数中的两个错误，它应该可以工作。

但是，如果您在另一个PL / PGSQL函数中尝试select correct_col_names()，则会得到相同的错误，因为select语句实际上正在执行任何结果。 perform correct_col_names()可以正常运行，因为PERFORM是PL / PGSQL语法，用于在您不想保存结果时调用某些内容。

pgsql sql函数顺序执行

1 个答案: