創建使用執行（PLPGSQL）

Question

我想要返回基於表名主鍵的下一個值的函數功能：

CREATE OR REPLACE FUNCTION next_pk (_table varchar) RETURNS INTEGER AS $$ 
    BEGIN 
     RETURN EXECUTE 'SELECT COALESCE (MAX (primary_key), 0) + 1 FROM ' || quote_ident (_table) || ' limit 1'; 
    END; 
$$ LANGUAGE plpgsql; 

select next_pk ('myTable'); 

但它提供了以下錯誤：

ERROR: type "execute" does not exist 
LINE 1: SELECT EXECUTE 'SELECT COALESCE (MAX (primary_key), 0) + 1 F... 

任何線索？謝謝。

Answer 1

你需要整型變量，而「執行到」：

CREATE OR REPLACE FUNCTION next_pk (_table varchar) RETURNS INTEGER AS $$ 
DECLARE 
    result integer;  
BEGIN 
    EXECUTE 
     'SELECT COALESCE (MAX (primary_key), 0) + 1 FROM ' || quote_ident (_table) 
     INTO result; 
    RETURN result; 
END; 
$$ LANGUAGE plpgsql; 

select next_pk ('myTable');