PostgreSQL存储过程用法实战详解
本文实例讲述了postgreSQL存储过程用法。分享给大家供大家参考，具体如下：
转了N多的SQL语句,可是自己用时,却到处是坑啊,啊,啊!!!!!!!!!!!!!!!
想写一个获取表中最新ID值.
上代码
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);
下面要写个存储过程，以获取表中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;
–大家可以试一下，上面这个是会报错的
–select f_getNewID(‘department’,’ID’);
–出错！
看了官方文档，人家就是这么用的：
EXECUTE ‘SELECT count(*) FROM mytable WHERE inserted_by = $1 AND inserted <= $2’
INTO c
USING checked_user, checked_date;
你确定你看清楚了？？？？？
确定你读完读懂了说明书？？？？？
–这个看了？
—————————————
EXECUTE ‘SELECT count(*) FROM ‘
|| quote_ident(tabname)
|| ‘ WHERE inserted_by = $1 AND inserted <= $2’
INTO c
USING checked_user, checked_date;
–这个看了？
—————————————
EXECUTE ‘UPDATE tbl SET ‘
|| quote_ident(colname)
|| ‘ = ‘
|| quote_literal(newvalue)
|| ‘ WHERE key = ‘
|| quote_literal(keyvalue);
–=============================
–好吧， 我改
——————————————————
drop function f_getNewID(text,text);
create or replace function f_getNewID(myTableName 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 对象（表名、字段名等）是不可以直接用变量的，要用 quote_ident()
——————————————————-
postgres=# select f_getnewid(‘department’,’ID’);
–错误: 字段 “ID” 不存在
–第1行select max(“ID”) from department
^
–查询: select max(“ID”) from department
–背景: 在EXECUTE的第10行的PL/pgSQL函数f_getnewid(text,text)
–===============================
–什么情况，ID怎么会有双引号，引号，号，号？？？
———————————————————-
–这里要感谢大神：权宗亮@飞象数据
–改成这样：
postgres=# select f_getnewid(‘department’,’id’);
f_getnewid
————
2
(1 行记录)
—-终于成功了！大小写还有区别吗？？？ –but why? –当在命令行输入
CREATE TABLE role(
ID INT PRIMARY KEY NOT NULL,
r_name VARCHAR(50) NOT NULL,
r_paretnID INT NOT NULL DEFAULT 0
);
–结果在pgAdmin里看到的却是小写的
–同样，如果是在QUERY TOOLS 下用这样的语句创建还是 所有的字体名为小写
–如果我就想大写怎么办？？？？
–要这样写
CREATE TABLE “RoleUPER”(
“ID” INT PRIMARY KEY NOT NULL,
r_name VARCHAR(50) NOT NULL,
“r_paretnID” INT NOT NULL DEFAULT 0
);
–再用大象看看
可以了！
总结一下：
1、存储过程（FUNCITON）变量可以直接用 || 拼接。上面没有列出，下面给个栗子：
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、存储过程的对象不可以直接用变量，要用 quote_ident(objVar)
3、$1 $2是 FUNCTION 参数的顺序，如1中的 $1 $2交换，USING 后面的不换 结果 ：
select max(myTableName) from myFeildname
4、注意：SQL语句中的大写全部会变成小写，要想大写存大，必须要用双引号。
附：一个完整postgreSQL 存储过程示例
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, to_char( CURRENT_Date, ‘YYYY-MM-DD’), v_start_time, 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;
希望本文所述对大家PostgreSQL程序设计有所帮助。
