if
if 語句形式包含以下幾種：
IF … THEN … END IF
IF … THEN … ELSE … END IF
IF … THEN … ELSIF … THEN … ELSE … END IF

create or replace function test_if(i int) returns void as $$
DECLARE
BEGIN
-- 替換對(duì)應(yīng)if語句
END;
$$ LANGUAGE plpgsql;
IF … THEN … END IF
該示例當(dāng)輸入值i大于10時(shí)會(huì)打印 i的值為：%
if i > 10 then
raise notice 'i的值為：%', i;
end if;
IF … THEN … ELSE … END IF

if i > 10 then
raise notice 'i的值大于10';
else
raise notice 'i的值小于等于10';
end if;
IF … THEN … ELSIF … THEN … ELSE … END IF

if i > 10 then
raise notice 'i的值大于10';
elsif i = 5 then
raise notice 'i的值為5';
else
raise notice 'i的值小于等于10';
end if;

case
CASE ... WHEN ... THEN ... ELSE ... END CASE
CASE WHEN ... THEN ... ELSE ... END CASE

create or replace function test_case(i int) returns void as $$
DECLARE
BEGIN
-- 替換對(duì)應(yīng)case語句
END;
$$ LANGUAGE plpgsql;
CASE … WHEN … THEN … ELSE … END CASE
該示例當(dāng)輸入值i為1時(shí)會(huì)打印 i的值為1 ，當(dāng)輸入值為2時(shí)會(huì)打印 'i的值為2' ，否則會(huì)打印 i的值既不為1也不為2
case i
when 1,3 then
raise notice 'i的值為1';
when 2 then
raise notice 'i的值為2';
else
raise notice 'i的值既不為1也不為2';
end case;

CASE
WHEN i BETWEEN 0 AND 10 THEN
raise notice 'i的值在0-10之間';
WHEN i BETWEEN 11 AND 20 THEN
raise notice 'i的值在11-20之間';
else
raise notice 'i的值不在0-20之間';
END CASE;

[ <> ] LOOP
statements
END LOOP [ label ];

create or replace function test_loop(i int) returns int as $$
DECLARE
BEGIN
-- 替換對(duì)應(yīng)loop語句
END;
$$ LANGUAGE plpgsql;
exit 退出

LOOP
-- 一些計(jì)算
i = i + 1;
IF i > 10 THEN
EXIT; -- 退出循環(huán)
END IF;
END LOOP;
return i;
exit when 退出
該示例與上方示例效果一樣。
LOOP
-- 一些計(jì)算
i = i + 1;
EXIT WHEN i > 10; -- 和前一個(gè)例子相同的結(jié)果
END LOOP;
return i;
exit [lable]

create or replace function test_loop(i int) returns int as $$
<>
DECLARE
BEGIN
<>
DECLARE
BEGIN
<>
DECLARE
begin
LOOP
-- 一些計(jì)算
i = i + 1;
IF i > 10 THEN
EXIT twoblock; -- 退出循環(huán)
END IF;
END LOOP;
END;
i = 100;
END;
return i;
END;
$$ LANGUAGE plpgsql;
continue
CONTINUE [ label ] [ WHEN boolean-expression ];

LOOP
i = i + 1;
EXIT WHEN i > 10;
CONTINUE WHEN i = 5;
raise notice 'i的值為：%',i;
END LOOP;

[ <> ] WHILE boolean-expression LOOP
statements
END LOOP [ label ];
示例
示例函數(shù) test_，將下方示例語句復(fù)制到對(duì)應(yīng)位置即可進(jìn)行測(cè)試，下方所有循環(huán)都可以使用此函數(shù)測(cè)試。
create or replace function test_(i int) returns int as $$
DECLARE
BEGIN
-- 替換對(duì)應(yīng)循環(huán)語句
END;
$$ LANGUAGE plpgsql;
該示例輸入值為0，判斷i的值是否小于10，小于10則執(zhí)行+1，否則 return 。
WHILE i < 10 LOOP
i = i + 1;
END LOOP;
return i;

[ <> ] FOR name IN [ REVERSE ] expression .. expression [ BY expression ] LOOP
statements
END LOOP [ label ];

FOR i IN 1..10 LOOP
-- 我在循環(huán)中將取值 1,2,3,4,5,6,7,8,9,10
END LOOP;
FOR i IN REVERSE 10..1 LOOP
-- 我在循環(huán)中將取值 10,9,8,7,6,5,4,3,2,1
END LOOP;
FOR i IN REVERSE 10..1 BY 2 LOOP
-- 我在循環(huán)中將取值 10,8,6,4,2
END LOOP;
查詢結(jié)果循環(huán)（FOR…IN… ）
FOR…IN

[ <> ] FOR target IN query LOOP
statements
END LOOP [ label ];

create or replace function test_for_in() returns int as $$
DECLARE
cddm record;
BEGIN
RAISE NOTICE 'reading jcb_cddm...';
FOR cddm IN SELECT * FROM jcb_cddm limit 5 LOOP
RAISE NOTICE '場(chǎng)地代碼為：%，場(chǎng)地名稱為 %', cddm.dm, quote_ident(cddm.mc);
END LOOP;
return 1;
END;
$$ LANGUAGE plpgsql;

create or replace function test_for_in(dm varchar) returns int as $$
DECLARE
cddm record;
BEGIN
RAISE NOTICE 'reading jcb_cddm...';
FOR cddm IN execute 'SELECT * FROM jcb_cddm where dm = $1 limit 5' using dm LOOP
RAISE NOTICE '場(chǎng)地代碼為：%，場(chǎng)地名稱為 %', cddm.dm, quote_ident(cddm.mc);
END LOOP;
return 1;
END;
$$ LANGUAGE plpgsql;
數(shù)組循環(huán)（FOREACH ）
FOREACH語法結(jié)構(gòu)如下：
[ <> ] FOREACH target [ SLICE number ] IN ARRAY expression LOOP
statements
END LOOP [ label ];

CREATE FUNCTION test_sum(int[]) RETURNS int8 AS $$
DECLARE
s int8 := 0;
x int;
BEGIN
FOREACH x IN ARRAY $1
LOOP
s := s + x;
END LOOP;
RETURN s;
END;
$$ LANGUAGE plpgsql;

CREATE FUNCTION scan_rows(int[]) RETURNS void AS $$
DECLARE
x int[];
BEGIN
FOREACH x SLICE 1 IN ARRAY $1
LOOP
RAISE NOTICE 'row = %', x;
END LOOP;
END;
$$ LANGUAGE plpgsql;