PostgreSQL自定义函数并且调用方式

CREATE [OR REPLACE] FUNCTION function_name (arguments)
RETURNS return_datatype AS $variable_name$  
  DECLARE  
    declaration;  
    [...]  
  BEGIN  
    < function_body >  
    [...]  
    RETURN { variable_name | value }  
  END;  $variable_name$ LANGUAGE plpgsql;

RAISE LEVEL 'format' [,expression,[...]]

FORMAT(format_string [, format_arg [, ...] ])

SELECT FORMAT('Hello, %s', 'world!!');

create or replace function ftest(in fname VARCHAR default '编程语言', cname VARCHAR DEFAULT 'java')
RETURNS VARCHAR as $$
begin
	 return format('%s_%s',fname,cname);
end; $$ LANGUAGE plpgsql;

select ftest('语言');  --语言_java
select ftest(cname=>'java'); --编程语言_java

CREATE 
	OR REPLACE FUNCTION testdivision ( js1 INT, js2 INT ) RETURNS INT AS $$ DECLARE
	v_re INT;
BEGIN
		raise notice'% 除以 %',
		js1,
		js2;
	IF
		js2 = 0 THEN
			raise EXCEPTION '不能除0';
		ELSE v_re := js1 / js2;
		RETURN v_re;
	END IF;
	EXCEPTION --捕获异常
	WHEN OTHERS THEN
		RETURN 0;
END;
$$ LANGUAGE plpgsql;

select testdivision(8,4);--2
select testdivision(3,0);--0

create or replace FUNCTION test1(in js1 int,inout res1 int,out res2 int) as
$$
begin
   res1:=js1*2;
	 res2:=res1*3;
end;
$$
LANGUAGE plpgsql;

select test1(3,2); --test1
                   --(6,18)
select * from test1(3,2);--res1|res2
                         --   6|  18

create table tmp(
 bsm VARCHAR(100),
 name VARCHAR(100),
 num int
);
insert into tmp(bsm,name,num) VALUES('a','苹果',21);
insert into tmp(bsm,name,num) VALUES('b','香蕉',11);

create or replace function getsum(in talename VARCHAR)
RETURNS int as $$
DECLARE
   stmt VARCHAR;
	 count int;
begin
  stmt:=format('select count(1) from %s', talename);
  raise notice '%',stmt;
	EXECUTE stmt into count;
	return count;
	EXCEPTION --捕获异常
	WHEN OTHERS THEN
		RETURN 0;
end; $$ LANGUAGE plpgsql;

select getsum('tmp');--2

create or replace function copytable(tablename varchar,times int)
RETURNS INT as $$
DECLARE
   stmt VARCHAR='create table %s_%s (like tmp including all);';--
begin
   for i in 1..times loop
	     raise notice 'd当前次数%',i;
			 raise notice '%',format(stmt,tablename,i,tablename);
			 EXECUTE format('drop table if EXISTS %s_%s;',tablename,i) ;
			 EXECUTE format(stmt,tablename,i,tablename) ;
	 end loop;
	 return 0;			
END; $$  LANGUAGE plpgsql;

select copytable('tmp',2);即复制tmp表2次