如何创建可以使用python脚本调用的postgresql函数？

我有一个任务，需要我从pgAdminIII中的表中提取多行，将行数据操纵成几个新的行类型（或者只是以某种方式生成数据）。如何创建可以使用python脚本调用的postgresql函数？

因为实际的操作似乎很难做到使用基本的sql命令，所以我决定尝试创建一个postgresql存储过程（或函数）。到目前为止，我所得到的都是语法错误。

我的PostgreSQL的功能：

CREATE FUNCTION getAllPayments(double precision, double precision, timestamp) RETURNS text AS $$ 
 
DECLARE 
 
credLim ALIAS FOR $1; 
 
paid ALIAS FOR $2; 
 
pdate ALIAS FOR $3; 
 
totalpayments double precision; 
 
numberofpayments integer; 
 
availablecredit double precision; 
 
BEGIN 
 
IF payments.customernumber = orders.customernumber THEN 
 
\t numberofpayments := COUNT(pdate); 
 
\t totalpayments := SUM(paid); 
 
\t availablecredit := credLim + totalpayments - numberofpayments; 
 
SELECT customers.customername, customers.customernumber, credLim, availablecredit, totalpayments, numberofpayments from customers, payments; 
 
ELSE 
 
Return "failed attempt"; 
 
END IF; 
 

 
END;

，这就是调用它的python脚本：

get_data = "getAllPayments(customers.creditlimit, payments.amount, payments.paymentdate)" 
 
seperator = "---------------------------------------------------------------------------------" 
 

 
crsr2 = conn.cursor() 
 
crsr2.execute(get_data) 
 

 
print('Customer Number Customer Name Payments Made Value of Orders Credit Limit Available Credit') 
 
print(seperator) 
 
for x in crsr2: 
 
    neu = str(x) 
 
    w = neu.replace(', ', ',  ') 
 
    print(w) 
 
print(seperator)

来源

2014-10-22 teutonic_surf_777

这并没有回答这个问题，但我忍不住发表评论：为什么不直接从PostgreSQL中检索所有数据，然后在Python中操作数据？当然，Python比PostgreSQL过程更容易使用？ – wookie919 2014-10-22 01:18:36

我看

ERROR: unterminated dollar-quoted string at or near "$$

终止该字符串，并告诉dbms您正在使用哪种语言。

CREATE FUNCTION getAllPayments(double precision, double precision, timestamp) 
RETURNS text AS $$ 
DECLARE 
    credLim ALIAS FOR $1; 
    paid ALIAS FOR $2; 
    pdate ALIAS FOR $3; 
    totalpayments double precision; 
    numberofpayments integer; 
    availablecredit double precision; 
BEGIN 
    IF payments.customernumber = orders.customernumber THEN 
     numberofpayments := COUNT(pdate); 
     totalpayments := SUM(paid); 
     availablecredit := credLim + totalpayments - numberofpayments; 

     SELECT customers.customername, customers.customernumber, credLim, availablecredit, totalpayments, numberofpayments from customers, payments; 

    ELSE 
     Return "failed attempt"; 
    END IF; 
END; 
$$     -- Terminate the string. 
language plpgsql; -- Identify the language.

这应该让它编译。我没有尝试，看它是否是有道理的，但我注意到，该行

 availablecredit := credLim + totalpayments - numberofpayments;

看起来有点可疑，并且不使用ANSI连接通常是一个坏主意。

来源

2014-10-22 02:09:59

如何创建可以使用python脚本调用的postgresql函数？

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