PostgreSQL儲存過程用法實戰詳解
阿新 • • 發佈:2020-01-09
本文例項講述了postgreSQL儲存過程用法。分享給大家供大家參考,具體如下:
轉了N多的SQL語句,可是自己用時,卻到處是坑啊,啊,啊!!!!!!!!!!!!!!!
想寫一個獲取表中最新ID值.
上程式碼
CREATE TABLE department( ID INT PRIMARY KEY NOT NULL,d_code VARCHAR(50),d_name VARCHAR(50) NOT NULL,d_parentID INT NOT NULL DEFAULT 0 ); --insert into department values(1,'001','office'); --insert into department values(2,'002','office',1);
下面要寫個儲存過程,以獲取表中ID的最大值:
drop function f_getNewID(text,text); create or replace function f_getNewID(myTableName text,myFeildName text) returns integer as $$ declare mysql text; myID integer; begin mysql:='select max( $1 ) from $2'; execute mysql into myID using myFeildName,myTableName; if myID is null or myID=0 then return 1; else return myID+1; end if; end; $$ language plpgsql; --大家可以試一下,上面這個是會報錯的 --select f_getNewID('department','ID'); --出錯!
看了官方文件,人家就是這麼用的:
EXECUTE 'SELECT count(*) FROM mytable WHERE inserted_by = $1 AND inserted <= $2' INTO c USING checked_user,checked_date;
你確定你看清楚了?????
確定你讀完讀懂了說明書?????
--這個看了? --------------------------------------- EXECUTE 'SELECT count(*) FROM ' || quote_ident(tabname) || ' WHERE inserted_by = $1 AND inserted <= $2' INTO c USING checked_user,checked_date;
--這個看了? --------------------------------------- EXECUTE 'UPDATE tbl SET ' || quote_ident(colname) || ' = ' || quote_literal(newvalue) || ' WHERE key = ' || quote_literal(keyvalue); --============================= --好吧, 我改 ------------------------------------------------------ drop function f_getNewID(text,myFeildName text) returns integer as $$ declare mysql text; myID integer; begin mysql:='select max(' || quote_ident(myFeildName) ||') from ' || quote_ident(myTableName); execute mysql into myID; --using myTableName,myFeildName; if myID is null or myID=0 then return 1; else return myID+1; end if; end; $$ language plpgsql; --============================== --漂亮,成功了! --But Why? --注意 物件(表名、欄位名等)是不可以直接用變數的,要用 quote_ident() ------------------------------------------------------- postgres=# select f_getnewid('department','ID'); --錯誤: 欄位 "ID" 不存在 --第1行select max("ID") from department ^ --查詢: select max("ID") from department --背景: 在EXECUTE的第10行的PL/pgSQL函式f_getnewid(text,text) --=============================== --什麼情況,ID怎麼會有雙引號,引號,號,號??? ---------------------------------------------------------- --這裡要感謝大神:權宗亮@飛象資料 --改成這樣: postgres=# select f_getnewid('department','id'); f_getnewid ------------ 2 (1 行記錄) ----終於成功了!大小寫還有區別嗎??? --but why? --當在命令列輸入 CREATE TABLE role( ID INT PRIMARY KEY NOT NULL,r_name VARCHAR(50) NOT NULL,r_paretnID INT NOT NULL DEFAULT 0 ); --結果在pgAdmin裡看到的卻是小寫的
--同樣,如果是在QUERY TOOLS 下用這樣的語句建立還是 所有的字型名為小寫 --如果我就想大寫怎麼辦???? --要這樣寫 CREATE TABLE "RoleUPER"( "ID" INT PRIMARY KEY NOT NULL,"r_paretnID" INT NOT NULL DEFAULT 0 ); --再用大象看看
可以了!
總結一下:
1、儲存過程(FUNCITON)變數可以直接用 ||
拼接。上面沒有列出,下面給個栗子:
create or replace function f_getNewID(myTableName text,myFeildName text) returns integer as $$ declare mysql text; myID integer; begin mysql:='select max('|| $2 || ' ) from '||$1; execute mysql into myID using myFeildName,myTableName; if myID is null or myID=0 then return 1; else return myID+1; end if; end; $$ language plpgsql;
2、儲存過程的物件不可以直接用變數,要用 quote_ident(objVar)
3、$1 $2是 FUNCTION 引數的順序,如1中的 $1 $2交換,USING 後面的不換 結果 :
select max(myTableName) from myFeildname
4、注意:SQL語句中的大寫全部會變成小寫,要想大寫存大,必須要用雙引號。
附:一個完整postgreSQL 儲存過程示例
CREATE OR REPLACE FUNCTION mt_f_avl_oee_period(i_station character varying,i_type int) RETURNS integer AS $BODY$ DECLARE v_start_hour character varying; v_end_hour character varying; v_start_time character varying; v_end_time character varying; v_start_datetime timestamp; v_end_datetime timestamp; v_type int := 0; v_rtn int; /* v_test9_count int; v_test9_success int; v_runningtime double precision; v_availablerate double precision; */ BEGIN -- hour = even,minute > 30 -- exists -- if i_type = 1 then SELECT EXTRACT(HOUR FROM CURRENT_TIME - interval '2 hours' ) into v_start_hour; --two hours ago SELECT EXTRACT(HOUR FROM CURRENT_TIME ) into v_end_hour; --get 'hour' of current time select v_start_hour || ':30' into v_start_time; select v_end_hour || ':30' into v_end_time; select mt_f_avl_oee_period_e(i_station,to_char( CURRENT_Date,'YYYY-MM-DD'),v_start_time,v_end_time) into v_rtn; else SELECT EXTRACT(HOUR FROM CURRENT_TIME - interval '3 hours' ) into v_start_hour; SELECT EXTRACT(HOUR FROM CURRENT_TIME ) into v_end_hour; select v_start_hour || ':30' into v_start_time; select v_end_hour || ':00' into v_end_time; select mt_f_avl_oee_period_midnight(i_station,v_end_time) into v_rtn; end if; RETURN 1; EXCEPTION WHEN others THEN RAISE; RETURN 0; END; $BODY$ LANGUAGE plpgsql VOLATILE COST 100; ALTER FUNCTION mt_f_avl_oee_period(i_station character varying,i_type int) OWNER TO postgres;
希望本文所述對大家PostgreSQL程式設計有所幫助。