SQL 在plpgsql的循环中递增一个数字
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Incrementing a number in a loop in plpgsql
提问by CQM
I couldn't find this immediately from the examples. I want to increment a variable in a loop, in a function.
我无法立即从示例中找到这一点。我想在一个循环中增加一个变量，在一个函数中。
For instance:
例如：
DECLARE
iterator float4;
BEGIN
iterator = 1;
while iterator < 999
.....
iterator ++;
END;
How would this be done?
这将如何完成？
I was looking at this document about flow control:
http://www.postgresql.org/docs/8.4/static/plpgsql-control-structures.html
我正在查看有关流量控制的文档：http:
//www.postgresql.org/docs/8.4/static/plpgsql-control-structures.html
And none of them seem to be relevant for me, unless these are absolutely the only ways to simulate incrementing a variable.
它们似乎都与我无关，除非这些绝对是模拟增加变量的唯一方法。
回答by Erwin Brandstetter
To increment a variable in plpgsql:
在 plpgsql 中增加一个变量：
iterator := iterator + 1;
There is no ++operator.
没有++运营商。
About the assignment operator in plpgsql:
关于 plpgsql 中的赋值运算符：
Correct syntax for loops in PL/pgSQL in the manual.
Your code fragment would work like this:
你的代码片段会像这样工作：
DECLARE
iterator float4 := 1; -- we can init at declaration time
BEGIN
WHILE iterator < 999
LOOP
iterator := iterator + 1;
-- do stuff
END LOOP;
END;
Simpler, faster alternative with a FORloop:
使用FOR循环更简单、更快的替代方案：
FOR i in 1 .. 999 -- i is integer automatically, not float4
LOOP
-- do stuff
END LOOP;
The variable
nameis automatically defined as typeintegerand exists only inside the loop (any existing definition of the variable name is ignored within the loop).
变量
name自动定义为类型integer并且仅存在于循环内（循环内忽略变量名的任何现有定义）。
回答by albfan
For a sscce
对于一个sscce
DO $$
DECLARE
counter INTEGER := 0 ;
BEGIN
WHILE counter <= 5 LOOP
counter := counter + 1 ;
RAISE NOTICE 'Counter: %', counter;
END LOOP ;
END; $$
if you want to avoid declare variable (more concise)
如果你想避免声明变量（更简洁）
DO $$
BEGIN
FOR counter IN 1..5 LOOP
RAISE NOTICE 'Counter: %', counter;
END LOOP;
END; $$
