如何創建可以使用python腳本調用的postgresql函數？

我有一個任務，需要我從pgAdminIII中的表中提取多行，將行數據操縱成幾個新的行類型（或者只是以某種方式生成數據）。如何創建可以使用python腳本調用的postgresql函數？

因爲實際的操作似乎很難做到使用基本的sql命令，所以我決定嘗試創建一個postgresql存儲過程（或函數）。到目前爲止，我所得到的都是語法錯誤。

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;

，這就是調用它的python腳本：

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)

來源

2014-10-22 teutonic_surf_777

這並沒有回答這個問題，但我忍不住發表評論：爲什麼不直接從PostgreSQL中檢索所有數據，然後在Python中操作數據？當然，Python比PostgreSQL過程更容易使用？ – wookie919 2014-10-22 01:18:36

我看

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

終止該字符串，並告訴dbms您正在使用哪種語言。

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.

這應該讓它編譯。我沒有嘗試，看它是否是有道理的，但我注意到，該行

 availablecredit := credLim + totalpayments - numberofpayments;

看起來有點可疑，並且不使用ANSI連接通常是一個壞主意。

來源

2014-10-22 02:09:59

如何創建可以使用python腳本調用的postgresql函數？

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